There are a few details I find strange in all of this:
(1) The notes were attached to cars and porches with leather belts?! Who has that many leather belts? What kinds of connections might a person have to get access to that many belts? Do police still have the notes and belts?
(2) While many places report him being strangled with just his scarf, I read on his sister's twitter page that he was strangled with an inner tube. Was this just lying around? Was it taken from Bill's bike (seems an unlikely adaptation, in light of the need for speed). Or did the killer(s) carry it with him/them? Is it in evidence?
(3) IIRC, the prior attacks involved TWO males assaulting Bill. I wonder if the notes reflect one or two styles of handwriting. It seems reasonable to me to assume that, in this sleepy part of the world, the prior attacks, notes, and murder would all be connected. If that's the case, wouldn't both males also be involved in the murder?
(4) We know the note writer targeted many individuals. Were any of them also ever assaulted? Did the killer(s) plan a wider spree, only to be frightened off by the media and neighborhood response?
Just dumping thoughts on the table. It seems there could be some physical evidence to apply modern forensics to ...