NL25 Call river V 51/15

[MaltbyStu]

Only about 50 hands but he's very aggressive.
No idea what the flop bet means but he must have something when he calls.

I check the turn since I want to get to s/d and being c/r would be gross.

Do you call this river lead now the board is paired? I wasn't expecting such a large bet.

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

CO ($37)
Hero ($25)
SB ($47.25)
BB ($5.40)
UTG ($15.50)
MP ($29.50)

Preflop: Hero is Button with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, CO calls $0.25, <font color="#CC3333">Hero raises to $1.25</font>, <font color="#666666">1 fold</font>, BB calls $1, CO calls $1.

Flop: ($3.85) 4[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">CO bets $0.75</font>, <font color="#CC3333">Hero raises to $3</font>, BB folds, CO calls $2.25.

Turn: ($9.85) 8[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
CO checks, Hero checks.

River: ($9.85) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">CO bets $6