this is so stupid, its like the girlfirend isn't alive or anything? Its not like you can AT WILL " **** someone else's girlfriend". She has to be some of the highest level of skank/whore to sleep with another man while in a relationship. So if shes that bad, its not something to apologize about if you sleep with her. If you didn't do it, she would've done it with someone else 1 week later.
"Hey dude, i ****** your girlfriend last night, but it's ok because now you know that she's a whore, you should thank me for being such a good friend man!"
Probably some prick that wanted to mess with a bunch of people, because the pic was taken at a good height meaning this was in front of a large apartment complex most likely...