Overcall weirdness

[ggbman]

I cant fathom how this isnt a 3 bet after the CO raises. Given that it was checked around on the turn, and he most likely would have bet a spade draw there, i would think you're usually good. He could easily be raising a good ten here given the action and that you just called the river bet. The only thing i am concerned about is flopped set which he decided to slowplay and then he filled and gave a free card. Still a re-raise IMO.