I thought that it was possible that the culprit screamed instead of the victim, and took advantage of the panic it caused to run over to them and kill them, under the guise of seeing what happened. Who got to the body first wasn't made clear, I think.
I wrote down the train of thought that led to me solving the murders here: https://docs.google.com/document/d/15MobEUaJRZuDApsJfi936hlrjNZdPIxFLAlCjtVFDa8/...
Interesting. I kinda thought the narrative itself got around that idea, but I can see how you could slip through the purples, at the very least, if you assume a certain person is the culprit. Might tighten up the purples a bit to disallow that option completely.
Looking at your reasoning, it's also good to see that the intended hint on the third murder worked!
