William "Billy" Chapman was the main protagonist-turned-main antagonist of Silent Night, Deadly Night.
Billy's parents were killed by a thief dressed as Santa Clause. Billy survived by running off and hiding on the bushes. Several years later, Billy is told to put on a Santa suit for the kids at a toy store that he worked at after which he goes insane after he witnesses one of his co-workers possibly attempted to rape a female co-worker, as it reminded Billy of how the killer santa attempted to rape his mother. He kills both the man and the woman, he then proceeds to kill the owner of the store and the assistant manage. He then proceeds to kill two teenagers that were having sex on a pool table and kills a teen that was sleding down a hill after Billy ran into the woods from the police when a few cops caught Billy sneaking into the room of a little girl. Billy plans to return to the orphanage he was put in after his parents were killed, possibly to get revenge on Mother Superior for the way she treated Billy when he was a kid. Billy manages to kill a police officer sent to the orphanage to look for him. Billy was then shot twice in the back by the cheif of police, killing him. After he died, his brother coldly looked up at Mother Superior and says "naughty", indicating that he plans on avenging his brother. And so, Ricky, would return in the next two sequels and begin a killing spree himself to avenge his brother.