What's the Motive?

The only thing i can think is that he just, he just lost it. If we believe his wife's testimony that he was a violent and abusive man, that does make sense. But even still, if she had this bruising, weak old bruising, on her wrists, that even if you have a child by their wrists and you're shouting at them, obviously that's horrible, but you're not beating them to death like that. I don't know what the actual motive is. There was no incidents or records or reports of likesexual abuse,. She was going to out him for anything like that.