NL25 - K high flush in blind battle, river decision

[volition]

Party Poker No-Limit Hold'em, $0.25 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

CO ($5.72)
Button ($34.13)
SB ($23.08)
Hero ($35.19)
UTG ($24.25)
MP ($15.68)

Preflop: Hero is BB with K[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/heart.gif[/img].
<font color="#666666">4 folds</font>, SB completes, Hero checks.

Flop: ($0.62) 9[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $0.5</font>, <font color="#CC3333">Hero raises to $2</font>, SB calls $1.50.

Turn: ($4.62) 8[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets $4</font>, SB calls $4.

River: ($12.62) 8[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $5</font>, hero...

Villain is 13/9/3.33 over 99 hands.

So, I wasn't sure what to do on the river here. I think his betting actions are pretty odd here, with his check on the turn and then leading out on the river for less than half the pot. What do you think he has, and what should I do? Raise him all in? Just call?