$22 tourney on BV

Blinds are 30/60 and we have about 4200. In bb with a clubs, 3 hearts

Utg+2 limps
button calls
I check

Saw no reason to raise this pre in a very soft tourney. They both have right around starting, 5K. No real reads on them yet. No one has done crazy bv fish stuff yet.

Pot 210.

Flop is 2h, 3c, 4c.

I check
utg+2 checks
button bets 160

We both call. Pot 690.

Turn Ah. We check and it checks around, I feel very confident we are ahead.

River 9 s. I check, hoping to get one of them to bluff at it. Then I get my wish and UTG+2 bets 5200 into the 690 pot. Button folds.

WTF? I got my wish but now what do I do? I can't make any sense out of his sizing. It feels like a bluff to me.

I've been talking about this hand with a friend and we have different opinions on what to do. We are both of the opinion that it's early and the field is soft and that's what makes this decision tough. He's inclined to fold says its not worth the call at this point, and I'm inclined to call because I think UTG+2 rarely has the nuts here.

Would be an easy decision if I knew who the hell player 117 was.