Help an Omaha8 newb out - Why did villain call this river?

[guitarizt]

Why did villain call on the river? Is there something I'm missing? This is like my 50th hand of omaha8 ever.

PokerStars 0.02/0.04 Omaha/8 (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is UTG with 6[img]/images/graemlins/spade.gif[/img], 2[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/club.gif[/img].
<font color="#CC3333">Hero raises</font>, <font color="#CC3333">UTG+1 3-bets</font>, <font color="#666666">1 fold</font>, MP2 calls, <font color="#666666">2 folds</font>, Button calls, <font color="#666666">1 fold</font>, BB calls, <font color="#CC3333">Hero caps</font>, UTG+1 calls, MP2 calls, Button calls, BB calls.

Flop: (20.50 SB) J[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">UTG+1 raises</font>, MP2 folds, Button calls, BB folds, <font color="#CC3333">Hero 3-bets</font>, <font color="#CC3333">UTG+1 caps</font>, Button calls, Hero calls.

Turn: (16.25 BB) 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">UTG+1 raises</font>, Button calls, <font color="#CC3333">Hero 3-bets</font>, <font color="#CC3333">UTG+1 caps</font>, Button calls, Hero calls.

River: (28.25 BB) T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">UTG+1 raises</font>, Button folds, <font color="#CC3333">Hero 3-bets</font>, UTG+1 calls.

Final Pot: 34.25 BB

Results in white below: <font color="#FFFFFF">
Hero has 6s 2c 6h Ac (High: full house, sixes full of threes).
UTG+1 has 4d 9c Ad 2h (High: one pair, threes).
Outcome: Hero wins 34.25 BB. </font>