Freakish (2016)

During Saturday detention, bells ring signaling a containment drill and evacuation – not out of the ordinary for a town with a large chemical plant. The 20 students and the basketball coach retreat to the school fallout shelter for the duration of the drill. Only it’s not a drill… When the sirens stop and they return to the school lobby, they find their town has been decimated by an explosion. They see no signs of life outside their high school’s front doors. More frightening, those who were not in the bunker appear to be infected…”