Funny hand

[piguy24]

I know this isn't the place to bitch about bad beats and I'm not, I just thought this story was entertaining.
Preflop: I open raise in MP1 with 77 (suits unimportant), and a maniac just to my left 3-bets. Button (new player) cold-calls and I call.
Flop: 997
I check, maniac bets, button calls, I check-raise, maniac 3-bets, button calls, I 4-bet, maniac 5-bets (caps) ALL IN, button calls, I call.
Turn: 9
I check, button checks.
River 9
I check, button checks.
Button shows 66, maniac shows 86o for the 4 9's, 8 kicker, for the winner.