If there was little or no evidence left behind, that's an indication there was meticulous planning involved.
For example, look at Semmie Williams, the man who allegedly stabbed Ryan Rogers to death. Based on the videos he uploaded, he was clearly psychotic. Even though he moved his victim's body to a more secluded area, he left his headphones behind and when police caught him, Williams was still walking around with the victim's blood on a bandana in his backpack.
People who experience uncontrolled psychosis and act out violently, typically do so, spontaneously. Their acts of violence seldom involve premeditation; which is why they often get caught.
In Katie Janness' case, although there was rage involved, some of it was controlled. The letters FAT were lightly etched into her skin. The "curvilinear incised wound" to her left breast. Targeting her rainbow-colored, lower-back tattoo. Killing Bowie. Not getting caught on camera. In my opinion, this doesn't sound like a psychotic killer in a blind rage. It sounds like a somewhat organized sexual sadist and stone-cold psychopath.
I have a feeling this might be related to the Patrick Boland case. I believe the killer frequents Piedmont Park and may even cruise their for sex and/or drugs.