Four people are in critical condition after, police say, a high school student went on a rampage with two kitchen knives.
Police say 16-year-old Alex Hribal stabbed 20 fellow students and a security officer in a crowded hallway of his high school just outside of Pittsburgh.
Hribal was arraigned as an adult. He faces four counts of attempted homicide, 21 counts of aggravated assault, and a charge of having a weapon on school grounds.
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