Serious injuries reported in school stabbing in Pennsylvania (with video)

A stabbing spree at a Pittsburgh area high school has left as many as 20 students injured, some seriously.

The violent attack at Franklin Regional High School was first reported at 7:13 a.m. Wednesday. By 7:30 to 7:40 a.m., the situation was under control, NBC News has reported. The suspect, who is a sophomore at the school, is in police custody.

"I was walking into the school and a stampede of people were running after me," Kari Lee told NBC News. "They were screaming, 'Go to your cars! Go to your cars! Someone is stabbing people!'

"It was really scary but it happened so fast I didn't know what to think," Lee said. "I know two people undergoing surgery right now.”

The known injuries so far include chest, back and abdomen wounds; some of them were categorized as life-threatening.

The Murrysville high school, which has about 1,200 students, does not have metal detectors.