Getting 3bet on turn, but checked to on river

[Peter]

Opponent is unknown. This is a bet right?

Party Poker 10/20 Hold'em (5 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Peter is UTG with A[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Peter raises</font>, <font color="#666666">2 folds</font>, SB calls, BB calls.

Flop: (6 SB) J[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, BB checks, <font color="#CC3333">Peter bets</font>, <font color="#CC3333">SB raises</font>, BB folds, Peter calls.

Turn: (5 BB) 8[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets</font>, <font color="#CC3333">Peter raises</font>, <font color="#CC3333">SB 3-bets</font>, Peter calls.

River: (11 BB) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks,