The game is 1-3 NL. Hero has ~$250 as does villian. Villain is directly to the hero's right; I don't exactly recall button position but neither hero nor villain was on the button.
Pre-Flop: A couple people call $3. Action reaches the villain, who raises to $12. Next up is our hero who has KK.
Hero raises to $36, expecting to take down the pot. Everyone folds around to the villain, who pretty quickly goes all-in.
Villain has been aggressive and mostly tight. He's shown an occasional unexpected hand (a button raise with 3⋄6⋄ that turned into trips on the flop) but most shown hands are strong. I haven't seen him do anything stupid.
Question: Do you call the all-in?
The hero chose to fold given the opponent's image and not wanting to risk his whole stack. The opponent left right after the hand, commenting how the only way he could win was to bet. This makes me think I was ahead, although I'm still surprised he risked everything, unless he thought I was playing loose. In retrospect, I'm ~80% against a random hand so mathematically, it seems like calling was the right play but it just seemed so out of step with his image to risk his entire stack without the nuts.