A male sophomore described as "really shy"' went on a slashing and stabbing rampage Wednesday with two knives at a Murrysville, Pa., high school, injuring at least 19 students before he was subdued and handcuffed, police said.

At least eight people were hospitalized with serious injuries, many deep puncture wounds to the abdomen, hospital officials said.

Murrysville Police Chief Thomas Seefeld said the suspect, who was in custody, was being treated for injuries to his hand. He was subdued and handcuffed by a principal and a security guard, he said.

Seefeld said a fire alarm triggered during the incident at Franklin Regional High School prompted students to flee the building, likely keeping down the number of victims.

Mia Meixner, a sophomore, told USA TODAY that she putting her books away near the cafeteria when she heard a commotion and saw the male suspect "stabbing people on top of a freshman."

She said the suspect "just got up and ran away really fast." Meixner identified the suspect, but USA TODAY is withholding his name from publication.

"The freshman stood up, lifted up his shirt and he was gushing blood," Meixner said. "I also saw a senior girl ... and she was gushing blood down her arm."

Meixner, who described the suspect as "really shy," said he "always kept to himself."

"He didn't talk to many people," she said. "He wasn't mean or anything, he just wasn't outgoing."

Mexiner said the suspect did not appear to be targeting anyone in particular..

VIOLENCE: Recent incidents of stabbing deaths

Nicole Damico, a junior at the school, told USA TODAY she and a friend were at their lockers when the alarm went off. They then heard the principal on a walkie-talkie shouting for more ambulances.

"We saw two kids down the hall and it looked like they were okay fighting," she said. "I realized that one had a knife so we sprinted out of the school. One if my peers had blood everywhere and he asked me for help. I just froze and ran out of the school. After that there was chaos."

Damico said students on social media were getting threatened last night that they would be beaten or killed.

"Us kids have been through hell and back. It made me realize that anything could happen at anytime. It was just a regular day," she said.

At least eight people were hospitalized with serious injuries, said Mark Rubino of Forbes Hospital.

He said three students were still in surgery, and that five were being evaluated and that some of them may require surgery.

He said many of the victims have "deep penetrating injuries" to the lower abdomen and right flank.

Doctors said a female student saved the life of a stabbed classmate by applying pressure until medics arrived.

Hospital officials said a 60-year-old man, apparently the security guard, was hospitalized for a medical condition, but was not stabbed.

Murrysville is located about 15 miles east of Pittsburgh.