What makes someone kill?

[The Prototype]

I have found serial killers to be very interesting to read about, learning why they have killed so many and why they chose their methods, etc. There was an article I read from a psychology site that was investigating the mind of some of them.

There is also a brain study that suggests that serial killers have different brainwaves to normal people, they had studied the brains of some serial killers and normal brains. Usually it seemed that they were either from violent homes that had them assaulted as kids, or in Gacy's case suffered a serious head injury.

There is an interesting movie on John Wayne Gacy which is called 'Dear Mr Gacy' an author interviewed him and wrote a book on Gacy and then later he killed himself. I've not watched the movie as yet, I've read a lot about it and the work done by the author.

I am also reading 'Murder In The Mind' by Amanda Howard.

It'd be interesting to find out what drives a lot of people to kill, I mean other than some of the more obvious reasons, money, etc.

[HAL]

Give me a brief synopsis.