I decided to flat because 4betting looks extremely strong (I would rather do that as a bluff, as I think people overfold in this spot. I could be wrong).

I was planning on Xr flop but he checks back. Clearly I want to bet turn, but then he raises which is kind of unexpected. I dont really see much that would want to Xb flop and then R that 6. I think shipping is a mistake and I think I should have called as he is simply very polarized imo. I dont think he would take this line with JJ-KK. So were up against a draw/air or set/straight.

I didnt think a straight was likely given his preflop 3B. But then again the same goes for draws. So kind of unsure what he has here. So maybe 66 for a turned set is his most likely holding? A total spazz?