(Re: spoilers, if you're up to date in the endurance run (specifically, today's VJ Endurance Run, there should be no problem.)
Deadly Premonition is one of those sorts of games I love to think about, as a lot is implied and people are generally unreliable so you have to look at things objectively rather than trusting everything you're told.
It's not particularly important, but I've been quite interested about the identity of the old Raincoat Killer.
So anyway! That's my theory. :D It might not stand up to scrutiny and/or sidequest information, I don't know, but for now I'm sticking to it.