Guy Catches His Best Friend’s Wife Cheating with Another Man and Confronts Her

Some guy recently caught his best friend's wife cheating on him, and decided to confront her while recording it.  Now the video's up on YouTube.

It looks like she's out at a club or something, sitting at a table with her leg draped over the guy.  Then the friend walks up and calmly asks what's going on.  And she realizes she's caught, so she just says, "Yep, you KNOW [what's] going on."

Meanwhile, the guy she's with, who is apparently the bartender tries to hide his face by putting his phone in front of it and turning the flash on.

The guy taking the video refers to himself as the 'best man' so I'm not sure if this took place late after the reception or what?  In any case it's a terrible situation.  What would you do in a case like this?  Would you confront them or just tell your friend about it later?