Killer's mother question, spoilers
I've caught most of this movie about a half a dozen times now, and there's one thing I still don't get. Why did the killer kill his mother? She's not one of the first three murders in either the first or last versions, so why would he kill her in the middle version when he's not dead or not caught? And why in the middle, not first or last? Also, why would anyone suspect a cop who's mother was killed by a serial killer, as John suggested? I would think he would be the last person you would suspect.
It's been driving me nuts. Any explanations?