At least 60 schools in Michigan closed on Thursday after police warned of potential copycat killings following the Oxford High School shooting on Tuesday, which left four students dead and seven people wounded. On Thursday, prosecutors signaled they may soon bring criminal charges against the parents of the 15-year-old suspect. The boy’s father, James Crumbley, purchased the semi-automatic pistol used in the killing just days before the massacre. Prosecutors say the gun was in the boy’s backpack during a meeting with his parents and teachers just before the shooting to discuss reports of “concerning behavior.” After the meeting, the teen was allowed to return to class. Prosecutors also said Thursday they discovered videos on the boy’s cellphone made the night before the massacre in which he talked about shooting and killing students the next day.