Gay Friend.......?

I have a good buddy that I play football with and while in a late shower I came back to see him and another guy having in a bathroom stall. I didn't know my friend was gay - or bi-ual, and it kind of shocked me. I don't want to be weird around him, he's still my friend and for that he's a good pal to me. But I don't want to embarr him or be an 'idiot' like I see others who find out their friend is gay. He's still pretty darn masculine to me (though as it turns out he's the fem of the relationship) and a cool guy. Question is 1) I don't want to come across as a azz-hole, 2) I want to improve our friendship without him taking to a '' level 3) maybe I'm freaking out but, I've never had to talk to a friend that hasn't told me he's gay but I found out - do I say something first or does he? Again, he's a good friend, please help.