What I find interesting about this hand is that he still 3-bet on the river when a potential over card to QQ-TT hit. I think for a lot of people with these hands they would bet/call, but we also don't have a read on him. I'm going to say he had something like A5s, AA, or even worse for him 99. Also, there is always that outside chance that he raised with 55 in early position and just got ridiculously lucky.