An official says four students were believed to be seriously injured at a high school near Pittsburgh, where a student with a knife stabbed or slashed others, injuring as many as 20.
Westmoreland County emergency management spokesman Dan Stevens says not all of the 20 injured were cut by the knife, though most were.
Some suffered scrapes and cuts in the mayhem that ensued at Franklin Regional High School in Murrysville on Wednesday morning.
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