Okay, let's see if we got a timeline settled out. We know Tarrlok probably died first, also that with the note his murder was probably pre-planned. But why kill two people? The glitter was on Tarrlok AND the chemicals, so we can probably assume it's one killer. That's just move evidence to hide when you only need one kill to escape.

I think someone mentioned the idea already but what if Lynne stumbled on the body early?. That would explain why the body is laid out so nice. Like she was examining them. Also why her body was hidden so sloppily- the killer might have had to improvise in a hurry.