Yes, that can be part of OCD. I don't know why it happens, but if it's a case where you worry it's something you'd do, think outside your OCD. Would you [i]really[/] murder someone? Probably not. So, when those thoughts come, blow them off, saying to yourself, that's silly. I'd never do that. If it's images or thoughts of those things happening, just practice ignoring them. It isn't easy at first, but it can be learned. I did. They might still occur, but they lose their effectiveness and disappear more quickly when you don't bother with them.