There are times when doing the right thing really, really sucks. I think that is is one of them. Your personal closure has nothing to do with it. There is a cold blooded deliberate murderer on the streets. If you are the one person who can stop that or one of the only ones who can, you really must even if it it will hurt. And I'm so, very sorry.
If there is a god, I want to believe that there is a god. If there is not a god, I want to believe that there is no god.