I found out my daughter’s father is in a physically abusive relationship with his gf.

I’m worried for his well being and that she may be the type to get him locked up. He has screenshots of her threatening him to ruin his life. In the text he seems innocent but when we were together he has a way of being mentally abusive due to him not dealing with his trauma and finances so he can be irritable but he never hit me. He is a great person and all though he can be mentally abusive, never ever physical with me. I don’t take the man’s side but his gf is very young and mentally unstable. Do I say something??? I’m afraid for my daughter’s fathers well being. There’s more background to what he’s going through right now personally but let’s leave it here.