10:00 a.m.The principal of Opportunity, Alabama's high school finishes her speech, welcoming the entire student body to a new semester and encouraging them to excel and achieve.10:02 a.m.The students get up to leave the auditorium for their next class. 10:03The auditorium doors won't open.10:05Someone starts shooting.Told from four perspectives over the span of 54 harrowing minutes, terror reigns as one student's calculated revenge turns into the ultimate game of survival.