The city and people of Boston — indeed, the people of the world — are still confronting the aftermath of one of the saddest days in the city's history, and are in the process of mourning the victims, helping the survivors, and finding the perpetrators. At least 183 people were injured, 17 critically, and three people were killed from two bombs that exploded at the finish line of the Boston Marathon.

You can see our complete recap of Monday's events here, and follow our other Boston coverage here, but here is what we learned on Day Two — about the dead, the bombs, the elusive bomber or bombers, and much more. (Update, Wednesday morning: It's all quiet and somber on the news front today, though a doctor at Boston Medical Center said that of the hospital's 11 original patients in critical condition, just two were currently in that state — including a 5-year-old boy. The hospital also has 10 patients in serious condition and seven in fair condition. "I will not be happy until they are home," he said. "I will not be satisfied." Scroll down for more, and click here for updates on Day Three — the third victim, new photos as potential evidence, and more.)

The Latest

Tuesday night, in cruel echoes of a stubborn daytime before it, yielded precious but little new information the Boston bombs — and sad remembrances of one, two, and almost three of the dead. The New York Times published a compelling story of a young man who lost both of his legs in one of the many indelible images of Monday afternoon's attack. He's the same one who was photographed being wheeled from the site of the explosion to the medical tent, while a man wearing a cowboy hat appears to be keeping him alive. Apparently, the young victim's father didn't know his son was injured until he saw the photo.

At the end of a day in which the Federal Bureau of investigation admitted it was in the "infant" or "early stages" of tracking down the bomber or bombers and President Obama called the bombings "an act of terror," authorities also revealed more about the bombs themselves. Just before 10 p.m. Eastern time, the FBI revealed a pair of images — one showing a scrap of black nylon, the other a hunk of metal — that they believe were part of one of the bombs. (Scroll down to "The Bombs" section below, for more on an unfolding day in amateur forensics.) Even as doctors revealed actual details about bombs intended to maim human bodies as they pulled fragments from limbs, some have speculated that the fragments might contain DNA from the still unidentified attacker, though they agency is still struggling for leads. Law enforcement remains bullish about catching the terrorist. As Richard DesLauriers, the FBI special agent in charge of the investigation, put it, "Someone knows who did this."

We also learned — after meeting (albeit too late) 8-year-old Martin Richard and 29-year-old Krystle Campbell — a bit more about the third victim who remains unnamed. Despite the FBI agent in charge of the Boston bombing investigation saying that there was "not enough work done to make a notification for the next of kin for the third victim," the Associated Press reports that an "official at the consulate's press section, who was not authorized to give his name, said that one Chinese student was injured and another died in the blast." An announcement on Boston University's website says the third among the dead is from its graduate school of languages: "The student's name has not been released, pending permission to do so from the family," the announcement reads. The school clarified in a statement that earlier reports identifying the victim were not confirmed. The university president had previously written about the injury. Here is the statement from Tuesday night.

The White House has confirmed President Obama's trip to Boston on Thursday. Per the administration's travel plans: "On Thursday morning, the President will travel to Boston to speak at an interfaith service dedicated to those who were gravely wounded or killed in Monday's bombing near the finish line of the Boston Marathon."

Meanwhile, in the Bronx, as Boston waited for the return of its own beloved teams, the New York Yankees paid tribute to their rivals in Boston by singing "Sweet Caroline" in the seventh inning stretch, an old Red Sox tradition. Team across the Major League made similar gestures. There was a vigil in Boston; there were so many people who wanted to spread well wishes it had to be expanded to a bigger venue.

Highlights from the early evening law enforcement press conference:

FBI special Richard DesLauriers, on evidence: A device or devices have been recovered from the blast site and sent to Quantico for analysis — they include pieces of black nylon could be from a backback, plus BB guns and nails possibly in a pressure cooker device, and are headed to Quantico for analysis. Both of the explosives were placed in a dark colored bag or backpack. "It is difficult to determine specific components uses," he said. "We won't know until the laboratory completes its review." FBI is "postulating" that they would be heavy bags in order to carry a heavy load, and are asking for tips about suspicious persons with black bags or discussing explosive plans. DesLauriers refused to elaborate on reports of a circuit board as a detonator (see below), or on how much planning went in to the attack.

DesLauriers, on the bomber(s): The FBI had reviewed over 2,000 tips today by noon, with a "tremendous" amount of video submissions from around the crime scenes that are currently being analyzed in Boston, but they need more: "Regarding who might be suspected in this event, the investigation is in its infancy.... Some of our activity you might see, some of it you won't... At this time there are no claims of responsibility... the possibilities are wide open." The next press conference will be in the early afternoon Wednesday. Regarding suspect: "It could be a person, it could be persons." The investigation will "be pursued methodically, diligently, but with a sense of urgency. It's in its inf— early stages."

DesLauriers, on the unidentified victim: "There is not enough work done to make a notification for the next of kin for the third victim."

Governor Deval Patrick: "There is a need for blood on a sustained basis... Do not go and make a donation today, but next week and the week after that there will be an ongoing need for blood donations." An interfaith service with President Obama will held Thursday at 11 a.m. "There is not yet an identified suspect. These are times when all kinds of forces start to conspire and make  people think about categories of people... This community will continue to heal if we turn to each other and not on other people." Patrick would not elaborate if there had been specific threats. The National Guard will be gone "when they're not needed anymore." Random bag checks in the T subway system "will continue for the next day or so."

"Next year's marathon will be even bigger and better."

A favor from the governor: Victoria, a Northeastern student in the hospital because of a serious schrapnel blast, who was carried to safety by a firefighter, is looking for "Tyler," a National Guard veteran from Afghanistan or Iraq vet who showed her his own schrapnel wound to calm her down. Call 617-725-4000 to help Victoria.

Boston Police Commissioner Ed Davis: Of the security plan leading up to the marathon," Davis insists that "this particular plan was very well thought out and executed.... By the virtue of the type of event this is, you can't turn it into a police state." BPD had extra offices in place, "especially toward the end of the race," in anticipation of a bigger crowd. "This was a standard threat picture. We're certainly extra vigilant after 9/11, but there was nothing specific."

Gene Marquez, ATF: A sulfuric type smell "has been reported," but officials are not ready to confirm. Debris has been recovered at nearby buildings that "gives you a kind of a scope of the power of the blast."

More evening updates:

Boston's NBC affiliate, WHDH, is trying to put together some pieces of photograph evidence on its own, suggesting this may be the "bag or backpack" in question, with before and after photos:

ABC News is reporting, despite everything we've heard today from doctors and law enforcement officials about pressure cookers and BBs and nails, a new kind of forensics detail: "Explosive used in at least one Boston bomb was gunpowder..." Reuters also reports, by way of current and former counterrorism officials, that gunpowder and schrapnel were used in at least one of the devices.

The number of injured has risen to 183, according to CNN. Though reporter Ryan Sloane reports that 89 of the 183 people injured in the attack have been released. 

The Boston Globe's Shelley Murphy has more on the specifics of where one of the bombs was placed. A circuit board has been found, the one believed to have detonated the blasts, and a source had told Murphy they believed it might have have been used to detonate the devices.  Murphy adds that the bomb was actually placed across the street from where Gov. Deval Patrick had been sitting earlier:

The Victims

Now that time has passed to notify families, many of the victims' stories are starting to be revealed. Early on Tuesday morning, The Boston Globe identified the 8-year-old boy who was one of the three people killed by one of the blasts. His name is Martin Richard, and he lived in the Boston neighborhood of Dorchester. Martin's mother, Denise, and one of his sisters were also seriously injured and remain in the hospital with "grievous injuries." According to one report, the sister, who is six, lost one of her legs. Martin and the rest of his family were at the finish line to greet his father, William, who ran in the Marathon. (The Globe now reports that William Richard was present, but did not run in the actual Marathon.) Yahoo News reports the family was hit by the second blast after moving into the street to get away from the first explosion. (Images via Facebook/Lucia Brawley)

Friends and neighbors have begun leaving flowers and messages of condolence outside the Richard's home and in a nearby playground (via WHDH's Nancy Chen, who has more pictures.) 

Boston Marathon runner Megan Cloke leaves flowers on the door step of eight-year-old Martin Richard's home in the Dorchester neighborhood in Boston, Massachusetts April 16, 2013. (Photo by Brian Snyder/Reuters)

Apparently, there was some confusion online that Martin's mother was the actress Denise Richards, but the names are not the same. The father of Martin Richard did issue a brief statement:

"My dear son Martin has died from injuries sustained in the attack on Boston. My wife and daughter are both recovering from serious injuries. We thank our family and friends, those we know and those we have never met, for their thoughts and prayers. I ask that you continue to pray for my family as we remember Martin. We also ask for your patience and for your privacy as we work to simultaneously grieve and recover. Thank you."

The second victim has been identified as Krystle Campbell, a 29-year-old resident of Medford, north of Boston. She was not running in the race, but was a spectator, cheering on a friend. Another friend who was also with her was seriously injured, according to Campbell's father. In a terrible and tragic twist, the Campbell family was actually told by doctors at the hospital that Krystle had survived, WCVB-TV reports, and that it was her friend that had died. Campbell's parents did not realize this until they were allowed to see the patient. WCVB writes: 

When William and Patty Campbell were finally allowed in to see the patient, they realized it was not their daughter. “I said, ‘That’s not my daughter, that’s Karen! Where’s my daughter?’" Patty Campbell said.

The third victim is also reportedly a woman, reportedly a Chinese national, though no other information is available at this time. 

In another similar heartbreaking story of families waiting together at the finish line, The Globe tells of two adult brothers from the Boston area who were standing next to each other (and near the Richard family) when the bombs went off. Each of the brothers lost a leg in the explosion.

The New York Times offers a compelling account of the young man who was photographed being rushed away from the scene in a wheelchair, both of his legs gone. The victim's name is Jeff Bauman Jr., a 27-year-old spectator who likes to play guitar, and he barely survived the attack, after losing large amounts of blood. Bauman's family didn't know he'd been injured until they saw the graphic photograph on the news not long after the explosions. They praise Carlos Arrendondo, the father of a fallen soldier who was handing out American flags before the blast and found Jeff on the ground soon thereafter. In the photo, he appears to be holding one of Jeff's arteries as he was being wheeled to the medical tent. Referring to Arrendondo, Jeff's mother told The Times, "The man in the cowboy hat — he saved Jeff's life."

Among those who were injured, doctors say patients ranged in age from 3 to 71 and suffered a wide variety of injuries, from minor to severe cuts and bruises, burns, ear drum damage, head injuries, and some loss of limbs.

Doctors at Massachusetts General Hospital said during a morning briefing that they conducted four amputations, but hope to save two more people who were in danger of losing limbs. Most of the injuries were to the lower extremities, suggesting the bombs were low to the ground. They also announced that they pulled "pellets and nails" from patients and believe they came from the bombs. (Doctors at the Brigham and Women’s Hospital had the same conclusion about their patients. Ten of their patients, including a five-year-old are in critical condition.) The most serious injuries were to spectators, not runners. Several patients are still in danger, but the doctor in charge is hopeful that there will be no more deaths.

There are also many first-hand accounts from the survivors and witnesses emerging today. Here is one from a Saudi man was near the bombs when they went off. (He is not the same man who was questioned as a witness.)

On Tuesday night, vigils were held around the city, including one in Boston Common where attendees sang the "Star Spangled Banner" and "Amazing Grace." Hundreds gathered at a baseball field in Dorchester to remember Martin Richard and another in Boston Common. Louie Cohn, who attended the vigil in the Common, walked through the crowd carrying 26 daffodils — one "for the 26 miles of the Boston Marathon," she said.

Image via NBC's George Colli

The Investigation

The FBI has taken the lead in the investigation of the bombings and last night they executed a search warrant on an apartment in Revere, Massachusetts. Authorities did not disclose the nature of the warrant or what drew them to the apartment, but police were seen removing several large bags from the building after 2:00 a.m. 

The apartment reportedly belongs to the student from Saudi Arabia who was tackled by a bystander after the blast and is still in the hospital with injuries. Police have interviewed the student as a witness, but say that he is not considered a suspect at this time. They've also assured Saudi officials that that is the case. He was fully cooperative and said he was only running away from the scene because he was frightened.

The Boston Globe interviewed the Saudi student's roommate, who said,"I don’t think he could do that." The student has been identified as a 20-year-old devout Muslim from Medina, who was studying at an English language school in Boston. He has officially been cleared as a suspect, according to Fox News.

The area around the marathon finish remains shut down as an active crime scene and will likely stay that way throughout the day on Tuesday. (The map above shows the cordoned off area.) Dozens of bags were left scattered around the area, dropped by fleeing spectators, and police say that each one must be inspected before being removed from the scene.

On Tuesday morning, several top officials, led by Massachusetts Governor Deval Patrick led a news conference about the investigation, but offered very little in the way of new information. Gov. Patrick confirmed that "two and only two" explosive devices were found and any reports of other devices were not true. Also, there are no suspects in custody at this time.

The FBI also confirmed that were no threats made before the Marathon and no imminent threats since that time. The agent in charge did not comment on other aspects of the case, including details about the bombs themselves or how they were made and detonated.

Many other high-ranking officials spoke at the briefing and most asked the public to continue to send tips, including photographs and videos that might aid in the investigation. Investigators are obviously hoping that someone might have caught the bomber on tape in a way that they could be identified. Police Commissioner Ed Davis confirmed that there were 176 confirmed casualties  that presented at local hospitals, and three deaths.

Beyond that, not much was offered other than encouragement, support, and vows to find the bomber or bombers and bring them to justice. Here are some other quotes from the briefing:

Mayor Tom Menino: "Yesterday, terror was brought to the city of Boston.... Boston is a strong city. The city will get through this."

Mass. Senator Elizabeth Warren: "The president is actively involved."

Rick Deslauriers, FBI Special Agent in Charge:  "Our mission is clear: To bring to justice those responsible for the marathon bombing... Expect to see agents conducting the investigation throughout the Boston area. There are no known additional threats." He later added, "We will go to the end of the earth" in a "worldwide investigation."

Gene Marquez, ATF: "We have 30 forensic specialists en route or on scene." Rumors of as many as seven unexploded devices were not true. If you have photos or video, please contact authorities. "Crime scene will take several days to process."

Carmen Ortiz, U.S. Attorney: "This is an active and ongoing investigation."

Ed Davis, Boston Police Commissioner: "Units from New York and Baltimore" are helping. He says that securing all video in the area is "basic investigative protocol." He asked the public to submit photos, and to note the time they were taken.

Dan Conley, Boston District Attorney: "Make no mistake: an act of cowardice and of this severity cannot be justified or explained. It can only be answered."

A spokesperson for the Pakistani Taliban organization Tehreek-e-Taliban told The Daily Telegraph that his group was not responsible for the Boston attack. They have claimed credit for previous attacks on the United States, including a botched Times Square bombing in 2010. They are also the group who carried out the attempted assassination of 14-year-old activist Malala Yousafzai.

Boston officials announced that local police and firefighter's unions have offered a $50,000 reward for any information leading to the arrest of those responsible, per CNN, and CNN is quoting a "U.S. official" as saying there is no indication of involvement from al-Qaeda or other foreign terror groups based on intelligence reports that have been gathered so far. (Again, the Saudi man who was interviewed has also been cleared as a suspect, per Fox News.)

The Bombs

CBS News and the Associated Press have new updates on the bombs themselves. According to anonymous law enforcement sources, "the explosives were in 6-liter pressure cookers and placed in black duffel bags. The person says the explosives were placed on the ground and contained shards of metal, nails and ball bearings." Officials say they also found a circuit breaker that may have been used to trigger the bombs.

On Tuesday evening, Fox News broadcast images that appear to be remnants of the original pressure cooker bomb. The images show some scraps of black nylon and a mangled piece of metal that appears to be marked as evidence. The FBI followed up not long thereafter with its own pictures of the remnants, including one that appears to show a piece of the pressure cooker:

And another of black bag remnants:

Some experts say that the attack could've been much worse. "We were lucky that the bomber was not more sophisticated and did not create a more powerful bomb," Bradley Buckles, former director of the Bureau of Alcohol, Tobacco, Firearms and Explosives, told USA Today. "These types of devices can be constructed by almost anyone. It doesn't require a great deal of sophistication. It's fairly easy to learn the technology of developing and manufacturing these devices."

More Images

Sports Illustrated has revealed this week's cover (taken by The Boston Globe's John Tlumacki) featuring a powerful and arresting image from the Marathon, and the story of how it came together on such a short deadline.

This Week's Cover: BOSTON bit.ly/17E9KDY // twitter.com/SInow/status/3…

— Sports Illustrated (@SInow) April 16, 2013

Unclaimed runner's bags from the Boston Marathon are seen in Boston, Massachusetts April 15, 2013. (REUTERS/Jessica Rinaldi)

Here's a recently surfaced video of the explosions that was taken from the grandstand, via The New York Times.

The Next Marathon

Officials in London say they are reviewing the security procedures for this weekend's marathon, in light of the incident in Boston. Nearly 40,000 runners and more than 500,000 spectators are expected for Sunday's race, which is one of the six "major" world marathons, along with Boston. Obviously, security was already on high alert for such a major public event, as it will be for the funeral of Margaret Thatcher, which will be held tomorrow. However, London has also gotten used to securing these events after last summer's Olympics and the Queen's Jubilee festivities, which went off without incident. Prince Harry will present awards to the winners and is still planning to attend. Meanwhile, race organizers announced that runners will be encouraged to wear black ribbons and hold a moment of silence before the start.

Tuesday in Boston

Boston is "open for business" according to Mayor Thomas Menino, but there are a few places that won't be opening due to the blasts. It's spring break week for Boston Public Schools so all schools were already scheduled to be closed today. A few local colleges, including Emerson College and Berklee College of Music, are also closed today. All trains are running, but the station closest to the blasts, Copley Square, is closed. The JFK library, where fire broke out yesterday, will remain closed. Some downtown offices have limited access, so people who can do so are working from home.

Tonight's home game for the Boston Celtics has been canceled and will not be re-scheduled since the regular season ends Wednesday and it will not affect playoff seedings. It will be the first time since the 82-game season began in 1967, that an NBA team will not play the full schedule of games. 

President Obama has ordered U.S. flags across the nation to be blown at half-staff until Saturday.

Situation at Logan

Around 11:00 a.m. on Tuesday, a full ground stop was ordered at Boston's Logan Airport have a U.S. Airways flight that had just landed was on its way to Philadelphia Chicago was stopped on the tarmac and passengers evacuated. It's not known at the moment if the incident is related to the Marathon investigation, but police surrounded the jet on the runway and reportedly ordered two male passengers off, apparently because they were speaking Arabic.  (In a separate incident, a terminal at New York's LaGuaradia Airport was also evacuated after a suspicious package scare.) A passenger onboard at Logan tweeted that the situation is now all clear. (The situation at New York's LaGuardia airport also got the all clear.)

"An Act of Terror"

President Obama delivered a short address from the White House Press Room before noon, calling the attack a "heinous and cowardly act" and (for the first time) referring to it as act of terror. He didn't offer any other updates on the investigation, saying we don't yet know who is responsible or what their motive is. The president added that "all resources" are being deployed for the case. He did not take questions from the media.

(Photo by Pete Sousa, White House)

Here are some key passages from the President's statement:

This was a heinous and cowardly act.  And given what we now know about what took place, the FBI is investigating it as an act of terrorism.  Any time bombs are used to target innocent civilians it is an act of terror.  What we don’t yet know, however, is who carried out this attack, or why; whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual.  That's what we don't yet know. And clearly, we’re at the beginning of our investigation. ...

It will take time to follow every lead and determine what happened.  But we will find out.  We will find whoever harmed our citizens and we will bring them to justice... 

We also know this -- the American people refuse to be terrorized. ...

I know that even as we protect our people and aggressively pursue this investigation, the people of Boston will continue to respond in the same proud and heroic way that they have thus far -- and their fellow Americans will be right there with them. ...

What I’ve indicated to you is what we know now.  We know it was bombs that were set off.  We know that obviously they did some severe damage.  We do not know who did them.  We do not know whether this was an act of an organization or an individual or individuals.  We don’t have a sense of motive yet.  So everything else at this point is speculation.