Any stats/reads?
Readless, I'd say it's a fold OTR. Looks like a flopped set, not too many 2 pair combos out there, would be hard for him to have a T. Even semibluffs are hard for him to have. There's A3cc, A4cc, 98cc which might play this way; 64s which IMO would be more likely to x/c than x/r OTF, 34cc i guess is possible too. Once you call turn though, there's really not much you could have other than some medium PP, or Tx, and you're certainly not folding Tx OTR, so the shove OTR really looks like it's for value. Higher PPs wouldn't play like this either. You do beat maybe something like 57 that flopped 2 pair, but again i don't think villain would be bombing river once he gets counterfeited.
Unless... he's a total maniac in which stats/reads would be essential.

I generally go smaller otf and insta-muck vs. the raise. So I'm folding turn and folding river. I'm not only folding though, I'm laughing my ass off at severely exploiting villain and saying, "Thank you for saving me money."

Cant imagine folding 99 being anywhere near reasonable strategy versus flop raise, especially cbetting this flop with high frequency (what i think hero should do with his equity advantage here).

So i propably would play the same. Call flop/turn and folding river. Readless.