You don't know anything about his hormones, or anyone else's for that matter.
if he killed 33 people he must be severilly mentally ill and mental illnesses are caused by severe chronic chemical unbalance in brains. knowing this its not hard(atleast for me) to come to conclusion that he must have had a chemical unbalance in his brains.
how can you know what i know or what i dont know?
"Where wisdom reigns, there is no conflict between thinking and feeling."
— C.G. Jung