Another hand from my PS $20 180 person final table

Down to 3. SB has been tight throughout, but recently either made a good play on me, or I made a mistake and has come into some chips. BB plays lots of hands, is aggressive, but hasn't been spewing chips lately (he tried earlier many times and sucked out, thus all his chips). People not folding to my steals as much as earlier and no idea whether they have cards or not, so I got somewhat confused.

PokerStars No-Limit Hold'em Tourney, Big Blind is t4000 (3 handed) converter

SB (t83940)
BB (t107747)
Hero (t78313)

Preflop: Hero is Button with K[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/spade.gif[/img].
<font color="#CC3333">Hero raises to t12000</font>, <font color="#666666">1 fold</font>, BB calls t8000.

Flop: (t20400) T[img]/images/graemlins/heart.gif[/img], T[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets t12000</font>, <font color="#CC3333">BB raises to t24000</font>, <font color="#CC3333">Hero ???