Are you kidding me?
Go to the police/cops. Dude, this is serious stuff. You can't just let it go un-noticed like that. He shot and killed another man. That's just sad and wrong.
I really hope you are kidding, if not, then I would get out of your neighborhood. It's not safe being around f'ked up idiots that live near you. This is to that f'ked up idiot who killed that man