NL 25 flopped bottom two/tough river decision

[Havok]

Full Tilt Poker - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 6 Players - (LegoPoker HH Converter)

SB: $21.60
BB: $26.30
Hero (UTG): $76.75
MP: $24.20
CO: $26.70
BTN: $22.55

Preflop: Hero is dealt J[img]/images/graemlins/diamond.gif[/img] T[img]/images/graemlins/spade.gif[/img] (6 Players)
Hero calls $0.25, MP folds, <font color="red">CO raises to $1.10</font>, 3 folds, Hero calls $0.85

Flop: ($2.55) K[img]/images/graemlins/diamond.gif[/img] T[img]/images/graemlins/club.gif[/img] J[img]/images/graemlins/heart.gif[/img] (2 Players)
Hero checks, CO checks

Turn: ($2.55) 6[img]/images/graemlins/heart.gif[/img] (2 Players)
<font color="red">Hero bets $2.55</font>, <font color="red">CO raises to $5.10</font>, Hero calls $2.55

River: ($12.75) 5[img]/images/graemlins/spade.gif[/img] (2 Players)
Hero checks, <font color="red">CO bets all-in for $20.50</font>, [i]Hero?

CO really hasn't gotten out of line. He's been typical loose passive. This is the most aggressive I've seen him. Does anyone think he's bluffing? I hate flopping bottom two with such a coordinated board!!!!!