2/4 - Rivered Straight on Paired Board

[B1GF1SHY]

Party Poker (6 max, 6 handed) converter
CO (~$600) Seem like a decent player
BB (Hero) (~$700) I have a slightly loose image, have shown some bluffs
2/4 NL

Preflop:
CO raises to $16, I call in BB with 77.

Flop ($32): 6[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, CO bets $24.

Turn ($80): 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, CO bets $40, BB calls.


River: 5[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>

BB bets $120, CO raises thinks for 5 seconds and goes all-in $400, BB ???.