(2/5 cash) The hand is heads up to the flop and after the flop the action is all in, and call. After counting the amount of the all in the dealer begins to put the turn and river when the player who called the all in tables Aces. The player who originally made the all in bet is disgusted and weakly pushes his cards forward while the turn is being put out. After the river which is a board pairing ten the all in player reaches forward and turns over king ten for a rivered three of a kind cracking the aces. The player with aces is livid that the other players cards weren’t mucked before the turn and river and believes the pot should be awarded to him. My question is, should the dealer stop the runout, muck the players cards, and award the player with aces the pot without seeing a runout.
This is not so much a matter of rule as of dealer training and casino policy. If a player leaves his hand face down and unprotected, the dealer may muck it, but most are trained to do this only when the player has done so in response to a bet. Once both players are all in, both are entitled to see the runout, and there's no reason for the dealer to muck a hand unless the player really tries to throw it in the discards or something.
A second point to mention, though, is you say the player only exposes one card: that means nothing. In that case, the dealer should announce "best hand shown is aces", ask the other player to show his hand or muck it, and absolutely take it an muck it if unprotected, even if the single shown card is enough to win. A hand not shown completely does not exist.