First -- do you have any reads on the player? Is he tight, loose, weak, aggressive, etc.?

As for the hand:

On the turn, he's probably either semi-bluffing a strong draw or value-betting with a strong made hand. The size of the bet seems more like a value bet, so he might have a full house, or he's just expecting to be able to successfully shove-bluff a ton of river cards so he wants as much of your money in now while leaving a believable shove for the river.

I would fold the turn without any reads. At 5NL he's probably not bluffing and your hand suffers from very bad reverse implied odds.