4NL Is this KK a fold?

$0.02/$0.04 No Limit Holdem
weaktight.com
5 Players

Villain is 24/17 3bet 0 over 130 hands


Stacks:
UTG ($4)
Hero ($4.63)
BTN ($7.43)
SB ($4.98)
BB ($3)

Pre-Flop: ($0.06, 5 players) Hero is CO
1 fold, Hero raises to $0.16, BTN calls $0.16, 2 folds

He called initially so I expect a wide range 22+, AJo+, Axs, some SCs

Flop: ($0.38, 2 players)
Hero bets $0.32, BTN raises to $0.88, Hero raises to $2.40, BTN raises to $3.92
My raise was intended to scare any Ax type hands....but it didn't happen.
At this point I reckon he has air or a set. Is this a fold?