Twelve people were killed and eight others injured at the Washington Navy Yard on Monday morning, after 34-year-old Aaron Alexis, a former Navy reservist and contractor, opened fire inside a headquarters building. 

Per the Navy's official release, the gunman, later identified as Alexis, entered the Naval Sea Systems Command Headquarters building around 8:20 a.m. Monday morning, where roughly 3,000 people work, and opened fire on employees in the building. He was eventually shot and killed by police, who recovered a shotgun and two pistols as the scene. The gunman reportedly had a severe case of mental illness and a violent background, and appears to have been acting alone.

This is a developing story and will continue to update throughout the day on Tuesday as more information becomes available. Click here to read all of The Atlantic Wire's related coverage on the shooting.

THE LATEST (12:44 a.m., Sept. 18) CNN report that surveillance footage shows Alexis entering a bathroom in Building 197 with a bag, and then exiting with a shotgun (the network has not posted the footage online). It is believed he brought a disassembled gun into the building in the bag. He then headed to a high point in the building's atrium and opened fire.

(7:13 p.m.) President Obama, speaking to Telemundo on Tuesday, urged Congress to act after the latest mass shooting: 

"The fact that we do not have a firm enough background check system is something that makes us more vulnerable to these kinds of mass shootings...And, you know, I do get concerned that this becomes a ritual that we go through every three, four months, where we have these horrific mass shootings. Everybody expresses understandable horror. We all embrace the families and obviously our thoughts and prayers are with those families right now-- as they're absorbing this incredible loss. And yet we're not willing to take some basic actions that we know would make a difference."

2:10 p.m.: The FBI and local police just updated the media on the investigation, by reiterating that there are no other suspects and that shooter did have an AR-15 rifle during the assault. The FBI says the shotgun he used to carry out the attack was purchased lawfully in Virginia.

The FBI says Alexis had been staying at local hotel since September 7, and encouraged anyone one might have had contact with him between that day and this week to come forward, saying "No lead is too small." All 12 deceased victims have been positively identified, and the those who were wounded are expected to recover.

11:11 a.m.: Navy officials have also released more information about Alexis's service record. It seems he was cited at least eight times for "misconduct," during the four years in the Navy reserves, for reasons including "insubordination, disorderly conduct and multiple excessive absences from work." Despite his record, he was honorably discharged and then hired back as a private contractor, with his security clearance intact. (It was also renewed in July of this year, according to The Washington Post.)

(9:30 a.m.): Some new small, but important details, have emerged on Tuesday morning, as the investigation continues. The Associated Press reports that the shooter, who was discharged from the Naval Reserves, but continued to work as a military contractor, was treated as recently as last month for several mental illness, including paranoia and voices in his head. Also, the FBI has confirmed that he was not armed with an AR-15 assault rifle, as had been previously reported. A spokesperson says one shotgun and two pistols were recovered at the scene, and at least one of the pistols was apparently taken from a security guard who Alexis shot.

(2:00 a.m.) An eighth victim has been identified: Arthur Daniels, 51, a grandfather of nine who installed office furniture in government buildings.

(1:17 a.m.) The DC Police Department has lifted the shelter in place recommendation for people in the vicinity of the Navy Yard.

(12:40 a.m., Sept. 17) The Washington Post has posted its front-page profile of Alexis. It includes new insights from Oui Suthamtewakul, who Alexis worked for in Texas. Suthamtewakul describes Alexis as "a 13-year-old stuck in a 34-year-old body." In addition:

Suthamtewakul said Alexis “had a gun at all times” and fired a bullet through the wall of his room in the summer of 2012. “You’re gonna kill me,” the restaurateur told his friend. Alexis apologized and said it was an accident.

Alexis drank alcohol frequently and in large quantities, Suthamtewakul said: “He can start drinking at 9:30 in the morning. He drinks often and for fun, but it was never a problem.” Asked what he will remember about his friend, Suthamtewakul said, “Him with a Heineken.”

(10:52 p.m.) Seven of the victims names and ages were released by the MPD on Monday night. All are non-military. They are: 

  • Michael Arnold, 59
  • Sylvia Frasier, 53
  • Kathy Gaarde, 62
  • John Roger Johnson, 73
  • Frank Kohler, 50
  • Kenneth Bernard Proctor, 46
  • Vishnu Pandit, 61

The identity of a wounded police officer was also revealed: Scott Williams, a K-9 officer with 23 years of experience. 

(10:22 p.m.) As per the press conference, authorities have also established that Alexis entered the Navy Yard though a legitimate pass acquired through his contract work at the yard. 

(10:11 p.m.) D.C. Mayor Vincent Gray reiterated in a late-night press conference that a second shooter is very unlikely, although authorities haven't "ruled that out," he added. Gray added that the ages of the deceased range from 43 to 76 years of age. Authorities are in the process of notifying the families of the dead. Gray also updated the injury count: 8 were wounded and hospitalized in the attack. Three of those were shot, while the other five were either suffering from stress-related injuries or from falling in the chaos. 

The city has lifted the "shelter in place" order, according to D.C. Police Chief Cathy Lanier, now that police are comfortable that they can account for the single suspect in the shooting. Of the victims, Lanier added that there was no indication any of the victims were active duty military, and that at least one victim has been identified as a D.C. resident. 

(10:08 p.m.) A press conference is scheduled to begin any minute. In the mean time, the Washington Post has released an image of tomorrow's front page for the paper: 

(9:32 p.m.) Here's at least one connection between Alexis and the Navy Yard: the former member of the Navy reserve (he was discharged in 2011) worked for "The Experts," a contractor out of Hewlett Packard Enterprises. They had work at the Navy Yard. While HP's CEO speculated that Alexis may have obtained an access card through his work with "the Experts," that's not confirmed. 

Meanwhile, a report from the Department of Defense's Inspector General, due to be released soon, apparently will demonstrate that the Navy Yard had let is guard down towards outside contractors working at the facility. According to Time, the audit began in 2012, and was set for release within a month in August. Here's more: 

The audit shows a history of those with criminal records managing to bypass the Navy’s security. Fifty-two “convicted felons received routine unauthorized installation access, placing military personnel, attendants, civilians in installations at an increased security risk,” according to the audit.

According to the Washington Post, about 2,000 people are still at the Navy Yard on Monday night, waiting for processing so they can go home. Those still waiting are civilians. 

(6:51 p.m.) A report of what sounded like gun shots on the White House lawn late Monday afternoon sent an already high-alert D.C. into action with a security alert at the White House. But the sounds weren't from a gun — they were firecrackers, thrown over the fence by an unidentified person. 

Meanwhile, we've rounded up the latest on gunman Aaron Alexis here

(4:49 p.m.) The Guardian's Spencer Ackerman reports Alexis "served in the US Navy from May 2007 to January 2011, according to Rear Admiral John Kirby, the Navy's chief of information." For the majority of Alexis' time served he was stationed in Fort Worth, Texas. Alexis received the National Defense Service Medal and the Global War on Terrorism Service Medal despite never serving overseas. 

(4:29 p.m.) The FBI confirmed Aaron Alexis, 34, formerly of Fort Worth, Texas, was the shooter. The law enforcement agency posted a call for information about Alexis Monday afternoon.

(4:22 p.m.) D.C. mayor Vince Gray confirmed 13 people have died, including the shooter. "We don't know what the motive is at this stage... We don't have any reason at this stage to suspect terrorism," Gray told reporters. Law enforcement are still urging people who live around the Navy Yard to stay indoors until the outstanding person of interest is found. 

(3:41 p.m.) Defence Secretary Chuck Hagel just released this statement

I have been receiving regular updates on the shooting at the Washington Navy Yard, and continue to monitor the situation closely.  This is a tragic day for the Department of Defense, the national capital area, and the nation.  My thoughts and prayers are with the victims of this outrageous act of violence, their families, and all those affected by today's events.  I am grateful for the swift response of federal and local law enforcement, and for the professionalism of DoD personnel at the Navy Yard complex.  The Department of Defense will continue to offer its full assistance in the investigation of this terrible and senseless violence.

The Fort Worth Star-Telegram found some background information on the suspected shooter:

Tarrant County court records show Alexis was arrested in Sept. 2010 for allegedly discharging a firearm within a municipality. The records do not indicate that Alexis was ever formally charged in the case.

Later that same month, Tarrant County court records show that The Orion at Oak Hill apartments in Fort Worth began eviction efforts against Alexis.

(3:14 p.m.) Reuters and CBS both confirming Alexis is the deceased shooter. Senate was ordered to recess until tomorrow. Now the Senate building is on lockdown until at least 5 p.m. because of "uncertainty surrounding the shooting at the Navy Yard," according to an email from Senate Sergeant at Arms Timothy Gainer. There's no indication of a threat or that anyone in the Senate is targeted, but they're locking down as a precaution. 

Tonight's scheduled baseball game between the Washington Nationals and the Atlanta Braves was also postponed until tomorrow.

(2:42 p.m.) This seems to be the strongest possible case for a positive I.D. yet. Pete Williams says 34-year-old civilian contractor Aaron Alexis is the deceased shooter. 

But we should be wary after the earlier mix-up. This is, so far, unconfirmed by law enforcement officials. D.C. police also just confirmed one of the two suspected other shooters was not, in fact, involved in the shooting.

(2:07 p.m.) D.C. mayor Vince Gray just confirmed 12 people died as a result of the Navy Yard shooting. On a possibly terrorism connection: "We don't have any reason to think that at this stage, but we're continuing the investigation," Gray told reporters. MPD chief Cathy Lanier said the FBI will take over the investigation from now on. "Please stay out of the area, and remain in your homes," Lanier said, addressing civilians who live near the Navy Yard. Lanier explained they're searching for two other suspects because they were seen at the Navy Yard with firearms Monday morning. "We have reason to believe that these people may be involved, and we need to talk to them," she said.

(1:43 p.m.) Reuters reports four people died and eight other were injured, including two law enforcement officers, citing naval officials. CBS and NBC falsely identifying the shooter as a retired Navy Petty Officer was apparently caused by an I.D. card found on the scene. The deceased suspect has not yet been identified. 

(1:00 p.m.) CBS is now walking back its report on the suspect's identity: 

(12:41 p.m.) CBS News has this update on the deceased suspect: 

(12:36 p.m.) "We do know that several people have been shot, and some have been killed," Obama told reporters before his remarks about the U.N. report on Syrian chemical weapons use. "We are confronting yet another mass shooting."

(12:18 p.m.) CBS's Stephanie Lambidakis and ABC's Pierre Thomas report the shooter was a civilian Navy employee in his fifties who had "some kind of job issue," recently. "As far as we know this is an isolated incident" District of Columbia mayor Vincent Gray just told reporters. MPD Chief Cathy Lanier just confirmed "multiple" casualties, including one shooter. "We potentially have two other shooters that we have not located at this point. This is not confirmed," Lanier told reporters. The two other suspects are dressed in military style uniforms. 

Lanier and Gray would not confirm the number of people injured or deceased. 

(12:04 p.m.) The Associated Press reports six people are dead, citing naval officials. 

(11:44 a.m.): The AP, NBC News and ABC News are all reporting that the shooter, has been killed. It appears the initial reports of multiple gunmen were wrong, too. "No hard evidence, at this point, that there was more than one shooter," NBC's Pete Williams reports.

Original Post: There are reports indicating multiple shooters, though that's still not confirmed. Per the Navy's official release, someone entered the Naval Sea Systems Command Headquarters building around 8:20 a.m. Monday morning, where roughly 3,000 people work, and fired three shots. The Metropolitan Police Department, the Military Police and the Capitol Police are assisting with the response. There's a "shelter in place" order while law enforcement agencies enter the building to confront the shooter. 

Details are still sketchy but here's what we know. NBC News and the Washington City Paper report, per Metropolitan Police, that ten people are injured so far. The U.S. Navy indicates there may be fatalities. Again, per Metropolitan Police, CBS News reports one MPD officer and one base officer are among the injured. ABC7's Autria Godfrey reports an officer was shot in both legs and the gunman is carrying an assault rifle. Pentagon spokesperson George Little told the Guardian's Spencer Ackerman there has been "loss of life" at the Navy Yard but the numbers are still not clear.

Officials at the Washington Hospital Center said three victims are there, two civilians and one MPD officer, and they should survive their injuries. "Their chances for survival are very good," the official said

The Washington Post reports this is a multiple gunman situation: 

At least one of the shooters is “down,” police said mid-morning, but it was unclear whether that means the suspect has been arrested or shot. They said the other suspect remains at large, and police believe they have pinned down one between the third and fourth floors of one of the buildings on the installation in Southeast Washington.

The Post previously reported three shooters, though, so take this with a huge grain of salt. NBC News paints a completely different picture: 

The Associated Press and Reuters have clarified, slightly, where the multiple shooters reports possibly came from: 

As stated above, details are sketchy. It's unclear at this time what kind of weapons the gunman has with him. "I am struck by how little we know about this, given that it's been going on now for two hours," NBC's Pete Williams said on air. This was the first description of a shooter's appearance:

This shot shows the vast law enforcement response on scene at the Navy Yard right now: 

This story will update as we learn more.

[Inset image via DoDMedia on Wikimedia Commons]