Silent Night, Deadly Night (1984)

A young boy watches his parents killed by a thief in a Santa suit. He spends his youth in an orphanage, staying quietly to his self, but his mind is further bent by an ironhanded Mother Superior. He finally gets a job at a local store, where he finally snaps when he is required to wear a Santa suit, and goes on a killing spree that leads him slowly back to the orphanage.