Just found out a LTR cheated. She says she didn't and only stayed on his (her ex) couch (while drunk off her ass), but obviously that's a lie. Not worried about her, going to hard next. I've learned my lesson.

But this guy, her ex, is a guy I would've called a friend - distant, but we're still pretty much in relating friend circles. He doesn't seem like the type to cheat with her especially knowing that her and I were together, but I don't doubt they at least did something in the 4-5 hours they were together while she was drunk off her ass. How do I handle this interaction with him? Confront him? Hard next him too? Should I tell him why or just basically say to fuck off?