(Reuters) - A 16-year-old student wielding two knives went on a stabbing rampage in the hallways of a Pittsburgh-area high school early on Wednesday, injuring 21 people, about half of them seriously, officials said.
The attacker moved stealthily through Franklin Regional High School, stabbing his victims in the torso and slashing arms and faces before anyone realized what was happening, students and officials said. Some of the injured taken to nearby hospitals were in critical condition, doctors said.
Students described a scene of panic, with the school hastily evacuated after a fire alarm was pulled. The unidentified sophomore suspected in the attack was in police custody, said Tom Seefeld, chief of police in Murrysville, Pennsylvania.
The attacks began around 7:13 a.m. EDT in several classrooms and hallways of the school in Murrysville, 20 miles east of Pittsburgh, officials said.
An armed security officer subdued and arrested the attacker with help from the principal, Seefeld said.
Freshman Josh Frank said he did not initially realize that anyone had been stabbed, but fled when he heard screaming.
"He did it so stealthily that at first no one knew what was happening," Frank said. "We heard a girl scream bloody murder. Then two seniors were running down the hall and we followed them out of the school."
A total of 21 people, most of them 14 to 17 years old, were transported to area hospitals, four by medical helicopters. Several had life-threatening injuries, with nine in critical condition, hospital officials said.
"Patients who are stabbed in the abdomen and chest by definition have life-threatening injuries," said Chris Kauffman, director of trauma at Forbes Regional Hospital, where some of the injured were treated.
Doctors said a female student helped save a male schoolmate by applying pressure to his wound until emergency responders arrived.
"She displayed an amazing amount of composure to help that friend who was having pretty significant bleeding at that point," said Dr. Mark Rubino, of Forbes Regional Hospital.
The suspect was also being treated for injuries to his hands, Seefeld said.
As they were reunited with parents near the hilltop high school in the relatively affluent Pittsburgh suburb with a population of about 20,000, teens spoke about the incident.
Michael Float, an 18-year-old senior, described running down a staircase and finding a friend badly wounded.
"There was a pool of blood," Float said. "He had blood pouring down the right side of his stomach," and a teacher was applying pressure on the wound.
Zak Amsler, a 17-year-old junior, said the attack occurred just before his first class was about to begin.
"I saw a girl with blood running out of her sleeve," Amsler said as he waited to pick up his younger sister, a student at the nearby middle school. "It was pretty mind-blowing."
Pennsylvania Governor Tom Corbett said he had ordered state police to help local law enforcement respond to the incident. The FBI also said it had deployed agents to work with local law enforcement.
"As a parent and grandparent, I can think of nothing more distressing than senseless violence against children," Corbett said.
Gennaro Piraino, superintendent of the Franklin Regional School District, said the high school would be closed for the next two to three days while police conduct an investigation.