WPTV Newschannel 5 ·

MURRYSVILLE, Pennsylvania (CNN) -- High schooler Mia Meixner was tending to her locker at the start of her day, when a ruckus behind her got her attention. Two boys were scuffling on the floor. Nothing to worry about, she thought -- until she saw one of them lift his shirt, and blood gushed out of his stomach. He had been stabbed, Meixner said.