What to do with KK here

[Double Down]

9 handed at Commerce 400 NL game.
I am in the BB with red kings. Blinds are 5-10. Loose action. UTG, somewhat new player, so far seems pretty solid, raises to 30. He has 625, I have him covered by a few hundred. 5 players call. I reraise another 75. He reraises another 100. Everyone folds to the button who has $280. He thinks for a long time and calls, leaving him with about 100 bucks.
What to do here?
I feel like there's a good chance he has aces here, but his 100 rereraise could have just been to isolate with me because had he called the 75, everyone else would have as well.
If I raise him another 100, he would just call if he had aces so I still wouldn't know where I stood.

After a couple minutes I called the 100.
Flop came 249 with 2 hearts. I check, he thinks for a few seconds and pushes all in his remaining 430. Button calls with his last hundred bucks. What do you do here?