That's definitely an interesting start to your story. It will be interesting to see more about this killer and who/what he is and what his motivations are. He sounds like a fanatic of one of the more extreme Christian fundamentalist belief sets; with a desire to force everyone to believe, and act, his way. It's going to be interesting to see how long it takes the wizarding world to wake up to this threat and deal with it. 'Twill be -real- interesting if he goes after Harry or one of Harry's friends or loved ones.