Some crazy. You know how you can tell it's some crazy dude and not a chupacabra or yeti or something like that (apart from the fact that those things don't exist)? Only domesticated dogs were gutted, no wolves. If this thing were so bad and so supernaturally powerful, he would gut wolves too. But it's just some lunatic who gets friendly dogs to approach him, then kills them.
People are so superstitious (except people on FR, of course, who are WAY too smart to fall for silly things like this!).