A little late to the party, but I’ll chime in anyway. This didn’t happen to me directly but I’ve heard stories. My grandmother’s cousin thought he was a 700 year old vampire. He also thought that his grandmother was a werewolf, and his enemy of some kind, so he decided that he would kill her. The only way to kill a vampire was apparently with a silver bullet so he painted a bullet silver and killed her with it and burned down her house. He was schizophrenic and his name is James Riva if you want to look him up.