Alex Hribal, the 16-year-old high school student accused of injuring more than 20 people at a Pennsylvania high school yesterday, has been charged with four counts of attempted murder and 21 counts of aggravated assault. He will be tried as an adult. 

Twenty-two people were injured at Murryville's Franklin Regional High School, including 21 students and one guard. One or two victims remain in critical condition.

AP Photo/Keith Srakocic

According to the Pittsburgh Post-Gazette, Hribal began attacking students with 8-inch knives before the school day began:

The incident began in a classroom in the school's science wing when the suspect pulled out two knives and started slashing and stabbing fellow students, said Mark Drear, vice president of Capital Asset Protection, which provides security guards for the school. Students, some of them wounded, ran from the room with the suspect chasing them a few hundred feet down a hallway. Many students were still at their lockers; some of them were attacked along the way, Mr. Drear said.

Officials are still looking into Hribal's motive, which for now remains something of a mystery. The Associated Press reports

"He wasn't saying anything," [attacked student Nate] Moore recalled hours later. "He didn't have any anger on his face. It was just a blank expression." At a brief hearing Wednesday night, District Attorney John Peck said that after he was taken into custody, Hribal made comments suggesting he wanted to die. 

AP Photo/Gene J. Puskar

Students and administrators were praised for how they handled the horrific situation, with one student singled out for saving her friend's life by applying pressure to her wound. Others followed procedure about as well as could have been expected under the circumstances, per the Post-Gazette

The practiced response protocol appeared to work effectively as school officials and security subdued the suspect, evacuated the school and quickly sought emergency help for the wounded.... The fact that a student pulled the fire alarm, [school director Roberta Cook] added, meant that he followed training recommendations to do so in any emergency so that students and staff would know to evacuate.

For now, Hribal is being held without bail at the Westmoreland County juvenile detention center.