Cowboys with a flush draw on a monochrome flop

[Mr. Curious]

300-500 live NL game
9 handed
Blinds are 5/10
Maximum bet is $500 (state law)

Stacks:
Hero $1050
Villian $850
BB $500

Hero is UTG+1 with K[img]/images/graemlins/club.gif[/img]K[img]/images/graemlins/heart.gif[/img]

Preflop:
UTG (semi loose, very weak) calls, Hero raises to $50, MP1 folds, MP2 folds, Villian calls, CO folds, Button folds, SB folds, BB calls, UTG folds

Villian is very loose, very aggressive, and very tricky. He likes to trap and will call with very marginal holdings. He might think about pot odds, but doesn't consider implied odds, reverse implied odds, or domination. His call could mean any ace, any pair, any connecter type (suited, one or two gapper). I think that he would have re-raised with AK, AA, KK, or QQ.

BB is a bad and very straight forward player.

Flop: 9[img]/images/graemlins/club.gif[/img]6[img]/images/graemlins/club.gif[/img]4[img]/images/graemlins/club.gif[/img] (3 players)
Pot: $160

BB checks, Hero bets $100, MP3 raises to $600, BB folds, Hero ...?