(USA TODAY) -- A male sophomore described as "really shy"' went on a slashing and stabbing rampage Wednesday with two kitchen 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 with deep puncture wounds to the abdomen, hospital officials said.
Doctors said a 17-year-old male student was in critical condition after being stabbed in his liver, diaphragm and major blood vessels, but that the blade missed his heart and aorta during the attack.
Murrysville Police Chief Thomas Seefeld said the suspect, who is in custody, was being treated for injuries to his hand. The 16-year-old sophomore was tackled by Assistant Principal Sam King and handcuffed by 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. The attack in classrooms and a hallway occurred shortly after 7 a.m., before classes began.
Sophomore Trinity McCool told USA TODAY that the suspect, after attacking several other people nearby, took a swipe at her and friend with what looked like a butcher knife.
"I saw his face, the look in his eyes, I was horrified," she said.
Another student, Nate Scimio, blocked the attack, however, by sticking out his arm as the blade came down.
"(Nate) took the stab right in his arm and saved my friend and me," McCool said. "I'm pretty sure it was his instinct. He didn't want anyone to get hurt. He told everybody to run away."
McCool said Scimio also apparently set off the fire alarm that sent students rushing to the exits. Scimio later tweeted a selfie from the hospital showing his right arm in a bandage.
Mia Meixner, a sophomore, told USA TODAY that she was 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.
At least 20 people are stabbed at a high school in the U.S. state of Pennsylvania. Video provided by Reuters Newslook
Sophomore Cameron Lazor said he came upon students screaming and fighting at the intersection of two hallways, then noticed to his horror that "people were bleeding." Then, he said, the suspect ran off down the hall.
"I saw that he was carrying two knives that were the big knives you find in your kitchen," Lazor told USA TODAY. "He wasn't saying anything. He started running and that's when we saw our classmates bleeding.
"At first we just thought it was a group of boys being immature and fighting," he said. "We looked around, saw the blood and it was scary."
Police said they have not established a motive for the stabbings.
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 play-fighting," she said. "I realized that one had a knife so we sprinted out of the school. One of 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.
All of the victims were students, ages 14 to 17. At least eight people were hospitalized with serious injuries, said Mark Rubino of Forbes Hospital.
He said three students underwent 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.
Rubino said a 15-year-old girl applied pressure to the abdomen of one of the victims to stop the bleeding until medics arrived.
"We're sure that played a role in his ability to be treated," Rubino said.
Hospital officials said a 60-year-old man, apparently the security guard, was hospitalized briefly and released.
Murrysville is located about 15 miles east of Pittsburgh.