I think he's trying a stop-n-go play. He's in early position, assumes you missed the flop with and AK, and he's shoving, hoping you'll fold. I'd call, you're way ahead most of the time, and if you're not you still have outs.
I agree with switch, if he'd flopped a set or even two pair, he'd wait to check raise you. Even most newbies, have enough savvy not lead out on their monsters, especially with you betting heavily preflop. Occasionally you will encounter an all-in push by a flopped set. The push is usually a way to disguise they have a monster hand. Who’s gonna push all-in with a flopped set, right? Sometimes it works, but it’s not a way to consistently get value for your top hands.