Bill is by no means a “typical” serial killer—if there is even such a thing. According to the FBI, a serial killer is someone who commits at least two murders over more than a month with an emotional cooling off period in between. The motive is psychological, often with sadistic sexual overtones. In Bill’s case, he was psychologically motivated to rape out of pent-up rage, and it appears that the sole motive behind all but one of the killings was to conceal the evidence of the rape.
