Speaking of Marty... he had a blood-covered item on him I don't recognize.

[ He gestures to a bloody handheld taser that's now sitting nearby him. ]

I found it in his pocket. I believe there was a possibility he could've used it or been forced to have used it in the duration of his actions that night.

One of his hands also had blood upon them -- though I believe it's easy to surmise from where that may have come from:

Those bloody messages.