UPDATE: 4:44 p.m.
Pennsylvania's governor says students at Franklin Regional High School acted heroically during today's stabbing spree.
Governor Tom Corbett says the fast reaction by students, police and emergency responders saved lives.
He also commended the school staff members for their quick thinking.
Police say an assistant principle tackled the 16-year-old suspect and a school resource officer got the student in handcuffs.
UPDATE: 4:21 p.m.
EXPORT, Pa. (AP) — Police have identified and charged a 16-year-old boy accused of stabbing and slashing 21 fellow students and a security guard at a Pennsylvania high school.
Authorities say Alex Hribal was being charged as an adult following the Wednesday morning attack in Murrysville, 15 miles east of Pittsburgh.
He appeared before Magisterial District Judge Charles Conway and was charged with four counts of attempted homicide and 21 counts of aggravated assault. He was shackled by his hands and feet and was dressed in a hospital gown.
The teenager's family lives in a two-story home with an attached garage in a nice subdivision of large, newer homes there. No one answered the door or phone calls.
The FBI was at the house Wednesday night. Neighbors say the teenager is the younger of the family's two boys.
UPDATE: 3:30 p.m.
Two victims of a stabbing rampage at a western-Pennsylvania high school are in critical condition.
Forbes Regional Dr. Mark Rubino says another victim is relatively stable and in surgery.
This morning's incident happened at Franklin Regional High School about 15 miles east of Pittsburgh. Police say they're questioning a tenth-grade male student.
The FBI says the computer of the 16-year-old suspect in today's high school stabbing spree has been confiscated.
Special Agent In Charge Scott Smith said agents continue to execute search warrants and electronic and physical evidence is being collected.
He also said there were surveillance video cameras in the school.
UPDATE: 1:45 p.m.
The suspect in custody
A police chief says 16-year-old boy "was flashing two knives around" when he injured 19 students -- four critically -- and a school police officer who eventually subdued him with the help of an assistant principal at a high school near Pittsburgh.
Murrysville police Chief Thomas Seefeld says the bloody crime scene left behind Wednesday at Franklin Regional High School is "vast'' and may take a couple of days to process.
Police have named Alex Hribal as the 10th-grade suspect who was taken into custody. He was taken to the hospital to be treated for minor wounds.
KDKA is reporting the teen will be tried as an adult in the stabbing rampage.
Two knives were used in the attacks, but the exact weapon type has not been released.
Investigators haven't determined a motive but say they're looking into reports of a threatening phone call between the suspect and another student the night before.
At least two of the victims were in critical condition, though doctors expect all victims to survive.
Just before 7:15 a.m. police received a call from a school resource officer asking for assistance in a stabbing.
An assistant principal of the school tackled the suspect while another student pulled the fire alarm, the Pittsburgh Post-Gazette reports.
A county emergency management spokesman says not all of the 20 injured were cut by the knife, though most were. Some suffered scrapes and cuts in the mayhem that ensued.
The high school will remain closed for the rest of the week.
Westmoreland County Emergency Director Dan Stevens called Franklin Regional High School in Murrysville a crime scene, and said it will be several days before classes resume.
The superintendent of Franklin Regional School District says his thoughts and prayers are with the injured and those affected by today's stabbing rampage.
Dr. Gennaro Piraino said counseling services are available for the entire school community.
Stevens said the FBI is on the scene assisting local authorities in the investigation.
Stay tuned to NewsRadio KFBK and KFBK.com for updates on this developing story.