Sophomore responsible for knife attack at Pennsylvania high school

UPDATE (3 p.m. EDT): Officials in Murrysville, Pa., still have not identified the knife-wielding student whose early morning attack left 20 people injured. Investigators have described the boy only as a 16-year-old sophomore.

Although they haven’t released any specifics about a possible motive, Police Chief Thomas Seefeld said his officers are looking into claims that the attacker might have been involved in a threatening phone call the night before. They don’t yet know whether he made or received the call or what it was about.

Only one adult appears to have been injured during the attack. The school security officer, who helped subdue the attacker, was treated at a local hospital and quickly released. Investigators say one of the high school’s assistant principals worked with the security officer to contain and eventually handcuff the attacker.

Not all of the 19 injured students suffered stab wounds. Some got cuts, scrapes, and bruises in their attempts to escape. Although several students remain in critical condition, doctors say all are expected to survive.

UPDATE (11:30 a.m. EDT): Officials now say the student responsible for this morning's knife attack is a sophomore. Murrysville Police Chief Thomas Seefeld said the school principal helped subdue the attacker, who was subsequently handcuffed by the school's resource officer. The attacker, who has not been named, is being treated for injuries to his hands.

OUR EARLIER REPORT (10:30 a.m. EDT): A male high school student in Pennsylvania walked into Franklin Regional Senior High School this morning and began stabbing his classmates, injuring at least 20 before he was taken into custody.

While doctors are treating teens with stab wounds to their torso, abdomen, chest, and back areas, investigators are trying to figure out what prompted the attack. The victims range in age from 14 to 17, and at least some of the injuries are life-threatening. A doctor at Forbes Regional Hospital in Monroeville, Pa., told CNN that emergency crews brought one adult to the facility for treatment as well. All of the victims are expected to survive.

Students not injured in the attack have been released to their parents. Other schools in the district, in Murrysville, about 15 miles east of downtown Pittsburgh, are closed for the day.