Video - National News
Posted on April 9, 2014 at 6:45 PM
Updated Wednesday, Apr 9 at 11:15 PM
Flailing away with two kitchen knives, a 16-year-old boy with a "blank expression" stabbed and slashed 21 students and a security guard in the crowded halls of his suburban Pittsburgh high school Wednesday before an assistant principal tackled him.
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Credit: Katrina Gutierrez / WFAA