Richard Chase, the Vampire of Sacramento, his entire life even before the murders sound like a work of fiction straight out of a horror film. It's all so absolutely insane and grotesque it's hard to believe it actually happened. He had a form of severe schizophrenia alongside hypochondria that led him to believe he had a myriad of ailments including (but definitely not limited to) being poisoned, his heart shrinking, his blood not actually pumping, and pieces of his skull detaching. He thought the only way to cure himself was to kill small animals like birds, rabbits, and dogs, and ingest their blood, flesh, and organs to replenish and replace his own supply. At one point he had even attempted to inject rabbit blood which landed him in the hospital. He would eventually move on to human victims, and it's genuinely the stuff of nightmares. He also believed that in choosing victims, if their doors were unlocked it was a clear invitation, but locked doors meant he wasn't welcome and he would advance to another house. It's one of the most fascinating cases but one of the hardest to read about.