SPRING VALLEY, N.Y. (CBSNewYork/AP) — A student stabbed multiple times and seriously injured Tuesday morning inside a high school in Rockland County.

As CBS2’s Dave Carlin reported, another teen has already been charged with the crime.

The stabbing happened around 8:45 a.m. at Spring Valley High School. The school was locked down afterward.

Police Chief Paul Modica said a 17-year-old boy was stabbed a total of four times and wounded in the arm, back, shoulder and side. The victim was taken to a hospital and was reported in serious condition. His injuries were not considered life-threatening.

Christopher Bermeo, 16, of Spring Valley, has been charged as an adult with attempted second-degree attempted murder.

Witnesses said the seriously injured victim managed to chase Bermeo out of the school. Investigators believe Bermeo dropped the knife as he ran away.

“The defendant took a taxicab to his house, and that’s where we found him,” said Spring Valley police Chief Paul Modica.

As the arrest went down, students were told not to move. Students and staff were kept behind locked classroom doors for more than an hour after the hallway altercation.

Armani Bent was in math class at the time.

“The teacher locked the windows, closed the doors, pulled down the blinds and we stayed in our class for a long time,” Bent said. “We were in second period, and we missed the third, and they told everyone to go to the fourth period class.”

Bent’s mother, Rhonda Payne, was shocked that someone was stabbed in the school.

“The school had called me first, said the school was in lockdown due to an incident but they said the students were safe,” she said. “Right after that, my son texted me saying there was a stabbing so how’s the student safe? So that made me angry and I came out here trying to get him.”

Students and teachers who said they know both teenagers involved said they had fought in the past.

“They brought their fight into the building, and that, unfortunately, gives everyone in the building a bad name,” said health teacher Lori Stiller.

At Bermeo’s arraignment, his attorney said the alleged offender was bullied and called the stabbing an act of self-defense. But parents were horrified by the violence.

“You come to school to get an education. Do so,” Payne said. “Don’t come to school for violence.”

Police said extra officers and security personnel will guard this school for the rest of the week.

Bermeo is being held on $500,000 bail.

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