KK vs large river bet?

[Bco1/75]

Hero is 25/4% up to this hand. He should have seen me as about 30/10%. I think my hand is good after the turn bet but he pots the river bet and ???? Typically a bet from nowhere means the last card had no impact on the players hand but???? Please let me know what you think if how I played this hand and what you think of the river bet....Call?


No-Limit Hold'em, $.25 BB (10 handed) FTR converter on zerodivide.cx

CO ($15.05)
Button ($14.15)
SB ($15.30)
BB ($19.80)
UTG ($24.35)
UTG+1 ($26.65)
UTG+2 ($16.90)
MP1 ($25.55)
MP2 ($60.70)
Hero ($39.95)

Preflop: Hero is MP3 with K[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/club.gif[/img].
[color=#666666]1 fold</font>, UTG+1 calls $0.25, UTG+2 calls $0.25, [color=#666666]1 fold</font>, MP2 calls $0.25, [color=#CC3333]Hero raises to $2</font>, [color=#666666]3 folds</font>, BB calls $1.75, UTG+1 folds, UTG+2 folds, MP2 folds.

Flop: ($4.85) 6[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/spade.gif[/img] [color=#0000FF](2 players)</font>
BB checks, [color=#CC3333]Hero bets $2.5</font>, BB calls $2.50.

Turn: ($9.85) 5[img]/images/graemlins/club.gif[/img] [color=#0000FF](2 players)</font>
BB checks, Hero checks.

River: ($9.85) 6[img]/images/graemlins/heart.gif[/img] [color=#0000FF](2 players)</font>
[color=#CC3333]BB bets $8</font>, Hero ?