weird AK hand

[udrazer]

SB is at seat 0 with $50.80.

hero is at seat 5 with $50.
The button is at seat 5.

SB posts the small blind of $.25.
BB posts the big blind of $.50.
hero: Ad Kd

Pre-flop:

player1 folds. player2 folds. hero raises to
$1.75. SB calls. player5 folds.

Flop (board: Ks Jc 6s):

SB bets $3. hero raises to $9.50. (after a long thought) SB
re-raises to $32.50. hero???
i thought he might have spade draw or such, but why he reraise so much? did he have 2 pair or set? i couldnt figure out.