[ceegee]

Unless you know his hole cards, he could be afraid of your board, paired his door card [2], and hit the river no?
This seems more likely as who plays 5th slow there with a 6 made already. If you really had a hand he's asking to get outdrawn to a potential wheel, although I doubt he could put you on a wheel draw on 3rd-4th. Still I think he made his hand on the river paired his door card paired his ace and hit the 3 on the river.