Being that the motives in the first 4 homicides were indeed sexual , not apparently anger motivated , and that this victim, who receives the most violent trauma of all 6 is not sexually assaulted, as with the previous 4 victims, where their shoes were missing, and not this victim, I'm inclined, based on these factors to say perhaps this killer was not involved in the first 4 and that the note claiming to be the same killer may just be throw LE off, but given what we are working with I could be wrong
Rsbbm.The 5th victim (Brenda Woodward) also the oldest victim at 18 is interesting and different, in which this victim is not sexually assaulted and is stabbed, now perhaps this was because she was older, stronger, and perhaps struggled with her killer, and he did what he needed to to control the situation, but theres no sexual assault listed, and unlike the other victims, she was covered up indicating perhaps remorse, or discomfort with this particular victim. But it can also have another meaning , in which the victim knows the killer
The lack of sexual assault is also interesting, was she too old for his liking? if that's the case, then why even abduct this particular victim, most Child killers abduct their victims based, on their apparent age , size, and lack of an adult presence, but the motive , is OVERWHELMINGLY sexual in those cases, this case at least to me seems out of sorts with the first 4, but we can only base this on what we know from the media .
Maybe the reason the perp took shoes from the SA young girls and not from the 18 year old, came down to the size of the shoe?
He might have been only sexually attracted to little feet/ shoes and repulsed by the (presumed) larger feet of the older girl (or whatever they represent to him) he brutally murders her and covers her up because he ''made a mistake''.
complete speculation, imo