At Least 20 Injured After Stabbings at Franklin Regional High School in Pennsylvania

At least four people with injuries Stevens described as "serious" were flown to area hospitals for treatment. He said some of the injured suffered stab wounds to the extremities.

Others were not actually stabbed, he said, and some of their injuries were cuts and scrapes.

The breakdown of injured and whether they were students or staff was not immediately known, but two hospitals reported nine patients ranging in age from 15 to 60. Among the victims was a security guard stabbed in the stomach, police said.

Alyssa Finch, who said she is a student at Franklin Regional High School, told ABC News a fellow student pulled the fire alarm during the stabbing "because he knew what was happening … and he wanted the people to get out."

The alleged stabber, whose identity has not been released, was in custody, according to Stevens. Police said he was 16 years old.

A statement posted on the Franklin Regional School District’s website said classes were cancelled today and that parents of middle school and high school students should report to Heritage Elementary for reunification. Any student who drove to school would not be released until a parent came to pick them up, the statement added.

Pennsylvania Gov. Tom Corbett said in a statement that he was "shocked and saddened" by the incident.

"As a parent and grandparent, I can think of nothing more distressing than senseless violence against children.

My heart and prayers go out to all the victims and their families," Corbett said. "I have directed the Pennsylvania State Police to assist local law enforcement in its investigation in any way possible. Other state resources will be made available to the community, if needed.

I assure the citizens of Murrysville that they have the full support of my administration."