Passive Turns Aggressive on Scary River

Villain is unpredictable. He's shown down some very questionable hands and is sometimes passive and sometimes aggressive. Very hard to put him on anything.

Party Poker 1/2 Hold'em (10 handed) FTR converter on zerodivide.cx

Preflop: Hero is BB with K[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/club.gif[/img].
<font color="#666666">6 folds</font>, <font color="#CC3333">CO raises</font>, <font color="#666666">1 fold</font>, SB calls, Hero calls.

Flop: (6 SB) 6[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/diamond.gif[/img], 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, CO calls, SB folds.

Turn: (4 BB) Q[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, CO calls.

River: (6 BB) T[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">CO raises</font>, Hero???

Ive got the second nut so there is no way I can fold. Is this a call or 3-bet?