I would definatlely call him on this and heres why. Look at his first 2 bets they are both just calls. could he be slow playing aa kk possibly but im thinking this guy to have maybe ak aj something along those lines. chances of him having a 3 or 4 out of all the remaining cards left in the deck not real high. right now i would be thinking i have the best hand after the flop and would have raised him before he went all in. Im thinking even if he where to go all in its money that i would have to put in the pot anyway so im going to raise him put pressure on him and maybe just maybe he folds and goes away.