QQ facing river overbet shove

villain is 77/11
not sure if he hit a draw, trying to get value from a 6, or just bluffing
seemed unusual for him

PokerStars No-Limit Hold'em, $0.25 BB (6 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

SB ($25)
BB ($29.20)
UTG ($38.10)
Hero (MP) ($55.95)
CO ($53.15)
Button ($32.55)

Preflop: Hero is MP with Qhttp://www.flopturnriver.com/phpBB2/...es/diamond.gif, Qhttp://www.flopturnriver.com/phpBB2/...iles/heart.gif
1 fold, Hero bets $1, 1 fold, Button calls $1, 2 folds

Flop: ($2.35) 6http://www.flopturnriver.com/phpBB2/...iles/spade.gif, 6http://www.flopturnriver.com/phpBB2/...es/diamond.gif, 10http://www.flopturnriver.com/phpBB2/...es/diamond.gif (2 players)
Hero bets $2, Button calls $2

Turn: ($6.35) 9http://www.flopturnriver.com/phpBB2/...iles/heart.gif (2 players)
Hero bets $4.50, Button calls $4.50

River: ($15.35) 8http://www.flopturnriver.com/phpBB2/...iles/spade.gif (2 players)
Hero checks, Button bets $25.05 (All-In), Hero folds

Total pot: $15.35 | Rake: $0.75

snap fold
even if he is bluffing a certain % of the time, it's more likely that he's pretty passive and this is for value a majority of the time and your hand is basically a bluff catcher because it can't beat any of his value range