Everyone has a reason to fear the boy with the gun.

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.

10:03 The auditorium doors won't open.

10:05 Someone 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.