Some people won't lay down a hand like AQ in this spot. He's already got 1500 of his 4200 stack in the middle when you jam. He knows he's made a bad move and is hoping that you're either bluffing, or he gets lucky.
The thing for me easy, and this is just my opinion, these types of hands will get you into a lot of trouble. KJ just plays very weak to a 3-bet potential. You've only got roughly 32 bb left and at the next level, you'll be at 24 or less. At that point, I would be looking for much stronger hands to enter in with. It's very conceivable that you'll be all in w/ that size of a stack, once the river bets are made, if not before. Is KJ a hand that you're willing to go the distance on once he 3-bets? It just screams that you're behind preflop to me.