[If he was a few seasons into his future he'd have a better answer here. He could tell you that monsters are humans who have been changed and that their souls are changed too and when they die they don't go to heaven or hell. They go to purgatory. As it is...] I'm not sure if it's that simple. Usually they feed on humans and kill them in the process without any remorse. And then one time we met a group of vampires who didn't kill to survive.