i have a theory on it all. so when he was a teen, he was supposed to be in bed asleep, or in the house at least. His dad came home drunk with some hooker, or took her to the barn or whatever. The kid who was mixed up anyway used to watch his dad fucking the whores, hidden away somewhere.
But one night his father had had a little to much to drink and as the whore was all naked in front of the dad trying to give him oral and little peter was jerking off, the dad could not get it up, the hooker mocked him and the father, known to be violent to women and children, lost it and punched the whore. He either kept up a sustained attack or accidently killed her.
The kid could do nothing without giving his hiding place away so had to sit in silence as his father dismembered the corpse whist possible fucking it at some point. Little peter continued to jerk off.
This would explain the dismembered body in the river when peter was just a kid, and why he chose that area of all places to set up his submarine project.
What he saw was such an intense visceral display that it imprinted on his young mind forever. The naked slut all bare before him showing him all he could ever want to see, but then the death and gore. No idea how he got turned on by dead, chopped up chicks but best guess is the trauma of it all fried his brain a little and the thing got mixed up in his arousal triggers.
So strong was the experience that he was never able to have a normal relationship, sexual or otherwise, with a woman in life. His only outlet was so called 'snuff' porn, faked or otherwise.
He thought he could trust his regular prostitute and maybe whilst drunk mentioned part of his fetish, as she was not repelled by the idea (I'm betting hookers hear all sorts of horrifying things, but have learnt to keep emotions hidden as to not piss of their client) he kept talking. Peter even went as far as suggesting to one prostitute they pair of them get a 3rd woman to torture and kill, which should have set the hookers alarm bells ringing but she must have been more interested in the cash)
As the prostitute had seemed ok with his disturbing 'pillow talk', it emboldened him, making him think that it was not such a sick fantasy after all. This then set in motion the build up to him getting a lone female on his sub.
He will have played the fantasy out in his head dozens, maybe hundreds of times whislt mastubating, each time tweaking it in his mind to make it the ultimate murder he could get away with.
Eventually when everything was in place he carried out the vile act. So faultless, specific and, in his narcissistic mind, perfect was the crime that he did not even think of a back up plan incase things went FUBA. It was the speed at which the random sailor came to rescue him, and the fact the man had a telescope that fucked the plan up. The rest is history.
What you think?