Need to help my friend

Hi I don’t really know what to do in this situation and am looking for some advice. One of my girlfriend’s best friends was dating this guy who originally went and sold her nudes on Yik yak at first she was ok with but she told him to stop and he did. That was a couple months ago, but now multiple girls have added have added her and given their story one girl who has been on and off with this guy for two years, says he has all her nudes and his blackmailing her threatening her saying if she says anything to anyone, he will post them and send them to our friends. He also has set up and only fans. without her knowledge( not my gf friends but this other girl) he is blackmailing these girls, and holding their nudes with threats of killing himself or posting the nudes if they do anything.