Turn straight in 3bet pot, river brings flush

[Irishman07]

Only have 60 or so hands on villain, but he has been very aggressive so far and is running at 34/24. Just decided to mix it up preflop and 3bet him. On the flop I didn't want to get c/raised off my draw and figured I could still make a play on the turn if I wanted.

I could have raised the turn but that looks like such a strong play and I think I force him off all but the top of his range. By just cold calling my hand looks weak and he can fire another barrel with a bluff on the river or he's likely to call a big bet on the river with any made hand since my line would look pretty strange betting the river. Unfortunately the flush hit and now I'm faced with a decision. His line does look a lot like a flush, but it also could be a bluff/maybe a set?

Full Tilt Poker No-Limit Hold'em, $2 BB (6 handed) Hand History converter Courtesy of PokerZion.com

saw flop|<font color="#C00000">saw showdown</font>

<font color="#C00000">MP ($294)</font>
<font color="#C00000">Hero ($228.60)</font>
Button ($138.90)
SB ($216.25)
BB ($81.65)
UTG ($214.20)

Preflop: Hero is CO with 7[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 fold</font>, <font color="#CC3333">MP raises to $7</font>, <font color="#CC3333">Hero raises to $24</font>, <font color="#666666">3 folds</font>, MP calls $17.

Flop: ($51) K[img]/images/graemlins/diamond.gif[/img], 5[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
MP checks, Hero checks.

Turn: ($51) 4[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP bets $40</font>, Hero calls $40.

River: ($131) T[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">MP bets $131</font>, Hero??