A sophomore at Franklin Regional High School in Murrysville, Pennsylvania, attacked his fellow students Wednesday morning, injuring at least 20 people, four of them seriously. He is now in police custody.

Dr. Chris Kaufman of Forbes Regional Medical Center said that two of the victims were in the operating room and a third would be going into surgery shortly. The rest of the injured were taken to University of Pittsburgh Medical Center hospitals, according to spokesperson Cindy McGrath. The attacker, whose name has not been revealed, also suffered wounds to his hands and is being treated.

Authorities said the attacker, who is 16 years old, used two knives during the assaults, which ended when assistant principal Sam King tackled and restrained him. The motive for the stabbings is unclear, said Murrysville police Chief Thomas Seefeld. "We don't know what led up to this," he said. "We're praying and hoping the best for all the victims."

Gracey Evans, a junior from Murrysville, which is about 20 miles east of Pittsburgh, gave a brief description of what she saw when she arrived at the school just before 7 a.m. EST. "I saw this kid in all black running down the hallway, stabbing," she said. "He was just stabbing everybody that was in his way."

This post will be updated as more information comes in.

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