MURRYSVILLE, Pa. (AP) — Flailing away with two knives, a 16-year-old boy with a "blank expression" stabbed and slashed 19 students and a police officer in the crowded halls of his suburban Pittsburgh high school Wednesday before an assistant principal tackled him.
At least five students were critically wounded, including a boy who was on a ventilator after a knife pierced his liver, missing his heart and aorta by only millimeters, doctors said.
The rampage — which came after years in which U.S. schools have geared much of their emergency planning toward mass shootings, not stabbings — set off a screaming stampede, left blood on the floor and walls, and brought teachers rushing to help the victims.
The motive was under investigation.
Police didn't immediately release the name of the suspect, who was taken into custody and treated for a minor hand wound.
The attack unfolded just minutes before the start of classes at 1,200-student Franklin Regional High School, 15 miles east of Pittsburgh. Police said it was over in just minutes.
Witnesses said the boy with the knives at first tackled a freshman and stabbed him in the belly, then got up and ran wildly down the hall, slashing other students.
Nate Moore, 15, said he saw the first attack and was going to try to break it up when the boy got up and slashed his face, requiring 11 stitches.
"It was really fast. It felt like he hit me with a wet rag because I felt the blood splash on my face. It spurted up on my forehead," he said.
The attacker "had the same expression on his face that he has every day, which was the freakiest part," Moore said. "He wasn't saying anything. He didn't have any anger on his face. It was just a blank expression."
Doctors said they expected all the victims to survive, despite large and deep puncture wounds to the abdomen in some cases. The wounded campus police officer was released.
Authorities credited an assistant principal with subduing the assailant, though they did not describe the end of the attack in detail. Students identified the assistant principal as Sam King.
A student, Ian Griffith, said he saw the school police officer confront the student, who then stabbed the officer. King then tackled the boy, Griffith told the Pittsburgh Tribune-Review.
King's son told The Associated Press that his father was treated at a hospital, though authorities have said he was not wounded by the knife.
"He says he's OK. He's a tough cookie and sometimes hides things, but I believe he's OK," Zack King said. The boy added: "I'm proud of him."
As for what set off the attack, Murrysville Police Chief Thomas Seefeld said investigators were looking into reports of a threatening phone call between the suspect and another student the night before. Seefeld didn't specify whether the suspect received or made the call.
Mia Meixner, 16, said the initial assault touched off a "stampede of kids" yelling, "Run! Get out of here! Someone has a knife!"
Michael Float, 18, said he had just gotten to school when he saw "blood all over the floor" and smeared on the wall near the main entrance. Then he saw a wounded student.
"He had his shirt pulled up and he was screaming, 'Help! Help!'" Float said. "He had a stab wound right at the top right of his stomach, blood pouring down."
Float said he saw a teacher applying pressure to the wound of another student.
Someone, possibly a student, pulled a fire alarm after seeing some of the stabbings, the police chief said. Although that created chaos, Seefeld said, it emptied out the school more quickly, and "that was a good thing that that was done."
Also, a girl with "an amazing amount of composure" applied pressure to a schoolmate's wounds and probably kept the victim from bleeding to death, said Dr. Mark Rubino at Forbes Regional Medical Center.
Public safety and school officials said an emergency plan worked as well as could be expected. The district conducted an emergency exercise three months ago and a full-scale drill about a year ago.
"We haven't lost a life and I think that's what we have to keep in mind," said county public safety spokesman Dan Stevens.
Associated Press writer Mike Rubinkam in Allentown contributed to this report.