[binions]

The problem with checking the flop and turn is that you have not defined your hand.

The guy could literally have anything. He may have interpreted your checking as weakness, as 2 scared Tens or Nines that will fold to a raise with 2 Kings on the board. He could make that bet on a scare board with a busted flush draw. Or he could have the nuts.

With so little information and only 12 possible hands ahead of you (3 ways to make 3 sets + 3 ways to make KJ -- discounting K5 and K2), there is no way I fold.