That is awful. I am so sorry to hear about this. I can't even imagine how shocked and horrified you must have been.
I have a male Sambava who started to rough up a receptive female Sambava one time. Fortunately, I was there and able to separate them before it went to far. He had climbed on top of her and was aggressively head butting her, for no apparent reason. It wasn't like she was trying to resist him.
Someone had a video, maybe on youtube of a case where 2 chams were placed together to breed and the owner left the room. he returned to find the male had the female in his mouth, by her midsection, and was thumping her up and down. She had been dead for sometime. The film sickened me, but I learned it could happen.
Thank you for letting us know about this awful experience. I have left breeders alone recently, forgetting about that video I saw. Now I realize what a risk it is. It's just that it's boring watching the two just lay there for a couple of hours. Even if you're across the room cleaning enclosures or mopping up, would a person be able to respond in time? It's possible there was nothing you could have done if you'd been there.
I cannot imagine what happens inside the brain of these males. Procreation instincts do them no good if they kill the recipient of their sperm. Must be a short circuit somewhere.