A 16-year-old boy was charged Wednesday after he allegedly stabbed 21 students and an adult -- leaving four seriously injured -- during an early-morning attack at a high school near Pittsburgh, authorities said.
Fox News has confirmed the identity of the suspect as Alex Hribal, a student at Franklin Regional Senior High School, the scene of the stabbing spree. The sophomore was being charged with four counts of attempted homicide, 21 counts of aggravated assault and one count of possessing a prohibited weapon on school property, according to a criminal complaint released by Westmoreland County District Attorney John Peck.
Westmoreland County Sheriff Jonathan Held described Hribal as quiet, adding that the teenager had not been talking to authorities since he was taken to be arraigned before a district judge Wednesday. He was jailed without bail.
Police said Assistant Principal Sam King tackled the boy and disarmed him, and a Murrysville police officer who is regularly assigned to the school handcuffed him.
King's son told The Associated Press that his father was treated at a hospital, though authorities said he was not knifed.
"He says he's OK. He's a tough cookie and sometimes hides things, but I believe he's OK," Zack King said. He added: "I'm proud of him."
As word of the incident spread and children streamed out of the school, parents told FoxNews.com they were shocked by the attack — and one district official expressed relief that it was carried out with a knife rather than a gun.
At a late afternoon press conference, Murrysville Police Chief Thomas Seefeld said "one or two" of the victims remained in critical condition.
He also said the suspect had been armed with two eight-to-ten inch straight knives.
“Nobody’s ever prepared for something like that as a parent,” Matt Provenzo, who had dropped his son, Mark, off at the high school moments after the stabbings, told FoxNews.com. "As he got out of the car, you could see students exiting the building and that the fire alarm was pulled … There were a few students who were visibly upset."
Another parent, Tim Graham, told FoxNews.com he picked up his daughter Alicia, who was not injured. But some of her friends were among those injured, he told FoxNews.com.
“She is with me and she was very close to the incident and a couple of her friends are stabbed," Graham said. "It could've very easily been my daughter."
Alicia Graham said she was in the school's library when the initial fire alarm went off.
"Everyone was screaming and people were being trampled over," she told FoxNews.com. "It was a very bad scene. I was very scared. I didn’t know what was happening. I thought it was a drill."
Alicia Graham characterized the suspect as a "small, skinny" classmate who didn't talk much. She didn't know him personally, but has acquaintances who do, she said.
Roberta Cook, a Franklin Regional School Board director and a member of its safety committee, said the local schools have well-practiced procedures in place for such events.
"But I'm just glad it wasn't a shooter, because if it had been a shooter, there would have been fatalities," Cook, whose children previously attended the school, told FoxNews.com.
A security guard at the school, in an affluent community about 15 miles east of Pittsburgh, notified authorities at 7:13 a.m. In all, the rampage lasted about five minutes.
The student's motive for the attack wasn't immediately clear, but Seefeld said investigators were checking reports of a threatening phone call between Hribal and another student the night before. He didn't say whether the suspect received or made the call. The FBI went to the boy's house, and local media reports said agents removed at least one computer along with other items.
Four of the victims were taken to area hospitals via helicopter. One victim was later identified as an adult and had been discharged, but no identities were immediately released. All of the victims are expected to survive, doctors told reporters during an afternoon press conference.
The overwhelming majority of students evacuated in a "remarkably orderly fashion," said Provenzo, whose son was not injured.
"I saw one or two [students] who were visibly upset," Provenzo told FoxNews.com.
Earlier Wednesday, Dr. Mark Rubino said eight victims were taken to Forbes Regional Medical Center, where three remained in surgery. Two other victims were listed in critical condition, he told reporters during a midday press conference.
"Most of them were to the lower abdomen and they seemed to actually almost have a pattern," Rubino said of the stab wounds. "Most of them were to the right lower abdomen and to the right flank and that created some of the criticality of their wounds and the nature of their injuries."
Seven teens and one adult were listed in serious condition at Forbes Hospital, West Penn Allegheny Health System spokeswoman Jennifer Davis said, ranging in age from 15 to 60. A ninth victim, a 15-year-old girl, was listed in good condition, she said.
Reese Jackson, the hospital's president and CEO, told the Pittsburgh Post-Gazette that one of the victims may have saved the life of another.
“A surgeon came out and congratulated one of the victims by saying she had saved the person’s life by applying pressure to the person’s wound,” Jackson told the newspaper.
Graham said the attacker, a sophomore whom he did not identify, had been a victim of bullying.
"My point is this could’ve been avoided," Graham told FoxNews.com, adding that his daughter had been previously assaulted at the school. "That's my personal opinion.”
Seefeld told reporters earlier a student or staff member at the school pulled a fire alarm when the attack began.
"The fire alarm being pulled probably assisted with evacuating the school," Seefeld said.
"There are a number of heroes in this day. Many of them are students," Pennsylvania Gov. Tom Corbett said in a visit to the stricken town. "Students who stayed with their friends and didn't leave their friends."
Fox News' Kristin Brown and The Associated Press contributed to this report.