Is it a good idea to let my friends know that a guy friend of mine used to abuse his ex?

My friend got out of a bad relationship where her bf abused her mentally and physically.. thing is, this guy is my friend too. She tells me all of the horrible things he’s done, but I haven’t seen his angry-side yet in person. I really want to warn my girly friends about him so they can be careful around him or better yet, keep their distance. Should this be my business or not? He’s already dating someone else right now and I fear for her.. Im afraid he may get violent with her.