So I thought they were.........

That would have been so stupid and ruined all the build-up for me. What's scariest is something that can really happen (and does) because it could be you.

Vampires. Fascinating. About as good as the cult theory. I would say that Vampires would not need so many victims and that this would be wasteful... but then again they don't explain why the cult needed to kill innocent people...

Not at all, I never got any feeling that something was supernatural or extraterrestrial or anything like that.