 He tells Theresa they must prevent David from killing more people at the school dance with a bomb he has planted in the school basement.Realizing the only way to stop David is by playing on the last sympathies he has towards them, Mark and Theresa enter the gym where the dance is being held and tell David that if he really wants to kill everyone then he will have to kill them too.David rushes to the basement and retrieves the bomb, and as he tries to defuse it, he takes it outside where it explodes, killing him.