MURRYSVILLE, Pa. (AP) — Doctors say one of the students wounded in a stabbing attack this morning at a Pennsylvania high school is on a ventilator, after a knife pierced his liver, missing his heart and aorta by just millimeters.

In all, at least five students were critically wounded and 15 other people were also hurt -- including a school police officer who confronted the assailant. The suspect is identified as a 16-year-old student. He's now in custody.

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A witness says he had a "blank expression" on his face as he flailed away with two knives in the hallway just before the start of classes this morning at Franklin Regional High School, 15 miles east of Pittsburgh. Police say the motive is under investigation.

Doctors say they expect all the victims to survive, despite large and deep puncture wounds to the abdomen in some cases. The wounded campus police officer has been released.

UPDATE: Suspect in school stabbings appears before judge

EXPORT, Pa. (AP) — A 16-year-old boy accused of stabbing and slashing 19 students and a police officer at a suburban Pittsburgh high school is appearing before a judge.

Authorities haven't identified the boy. But he appeared before Magisterial District Judge Charles Conway on Wednesday afternoon in Export, about 5 miles from the Murrysville high school. Charges are expected to be filed soon.

The boy was shackled by his hands and feet and was dressed in a hospital gown.

Witnesses say the boy tackled a freshman and stabbed him in the belly on Wednesday morning and then got up and ran wildly down a hall, slashing other students. They say he had a blank expression on his face before an assistant principal tackled him.