Lo que pensamos, lo que hicimos

While the students in Mr. Fuller's math class are taking a test, an alarm goes off signaling that someone has entered the school with a gun. The building goes into immediate lockdown. All of a sudden, there is a knock at the door. A little girl asks to be let in. Against policy, the class opens the door and the intruder gets inside. The story of what happens next is told alternatively by the teacher and two students.