The attacker, identified as Alex Hribal, was taken into custody by police and treated for a minor hand wound shortly after the incident.Twenty-one students and a security guard were stabbed early Wednesday by a 16-year-old boy student at a high school in the US state of Pennsylvania. Photo: Xinhua

 
A 16-year-old student wielding two knives went on a stabbing rampage in the hallways of a Pittsburgh-area high school on Wednesday, wounding 22 people before he was tackled by an assistant principal, officials said.

The attacker moved furtively through the halls of Franklin Regional High School in Murrysville, stabbing his victims in the torso and slashing their arms and faces, students and officials said. Some of the injured taken to nearby hospitals were listed in critical condition.

Alex Hribal, a 16-year-old sophomore, was taken into custody, said Captain Rob Liermann of the Murrysville Police Department.

Charged as an adult, Hribal faces four counts of attempted homicide and 21 counts of aggravated assault, Liermann said. He was ordered to face a preliminary hearing in seven to 10 days.

Students described a scene of panic, with the school hastily evacuated after a fire alarm was pulled.

"He did it so stealthily that at first no one knew what was happening," freshman Josh 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."

Assistant Principal Sam King tackled the boy, who was armed with two straight knives, and an armed security officer handcuffed him with help from King, said Murrysville Police Chief Thomas Seefeld.

Twenty-one students and a security officer were stabbed in the incident, said Dan Stevens, a spokesman for Westmoreland County emergency management. Two other students suffered minor injuries trying to get out of the school, Stevens added. He said the teenage suspect was not counted among the wounded.

Among those praised for heroics during the incident was Nate Scimio, the student who pulled the fire alarm and helped shield classmates, witnesses said.

"There's not enough words to describe how much of a hero he is," classmate Trinity McCool said on Facebook.

The victims, most of them 14 to 17 years old, were transported to area hospitals, four by medical helicopters. Several had life-threatening injuries, hospital officials said.

While the US has seen a number of large-scale school shootings in recent years, mass stabbings are less common.

Police and the FBI were searching the suspect's home, situated at the end of a quiet cul de sac. Neighbors said both parents work, and the teen has a brother who also attends Franklin Regional High School.

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 officials.

The high school will be closed for the next two to three days while police conduct an investigation, officials said.

Reuters