The 16-year old boy allegedly responsible for injuring 19 people at his Pennsylvania school this morning has given no clue as to why he would attack his schoolmates.

Alex Hribal brought two kitchen knives with him on Wednesday morning and went on a stabbing spree in the hallways of Franklin Regional High School, injuring nearly two dozen people before an assistant principal tackled him and wrestled the weapons away. Officials say he will be charged as an adult for the attack, but for now, there is no obvious motive. Those who knew him well say his family was well-regarded in the community and there are no reports of bullying, but authorities say they are investigating a possible “threatening phone call” between Hribal and another student that occurred earlier in the week.

Hribal’s schoolmates say he had been acting off lately, however.

“I know some people who knew him well and they can’t seem to put an exact pinpoint on what caused it,” 17-year old Matt DeCasare said. “I heard earlier this week when people tried to talk to him in Spanish class—I know one girl tried to talk to him and he seemed a little on edge, a little different than usual this week.”

Initial reports after the incident said that several victims were airlifted to a local hospital, and that four of those were seriously injured. Their condition is not known at this time.