G/f's ex hitting her literally

hey yall im with this one girl and shes my BEST friend and we have been going out for a year and I caught her and her ex and he was beating her and she got so many bruises and scars and I asked her and she lied to me and I want to BEAT HIS ASS SO BAD but she wont let me and she lied to me and I don't know wht to do I mean she lied shes being hurt and he tells her to break up with me or he wont stop so should I break up with her so she will stop going through pain

chances are he is still going to abuse her even if you 2 do break up. I sugjest seeking other help, like abuse clinics or even an adult. as for wanting to beat him up, don't do that, it will only cause more tension between the 3 of you. like I said, seek stronger help please!