As I've mentioned before, I write about serial killers, but mine don't even realize they're serial killers. In one novel, the killer does it for a distorted view of love. In another, the killer does it for revenge, and also to rid the world of animal abusers...a noble thing, but I digress.
I wonder how many serial killers don't realize what they are either. People like Ted Bundy must have known, because he was way too smart and crafty NOT to. Others actually DO it for the notoriety, like the Zodiac killer, who was never caught, even managing to taunt the authorities for decades.
Another one that comes to mind is the diabolical Henry H. Holmes, who built a hotel specifically for his murderous deeds, if you can believe it. (Henry H. Holmes)
This guy knew exactly what he was doing, even taking some of his own employees as victims.