I played a tournament in a casino when this happened to me. I was hold nothing and trying to bluff my way through it heads up against somebody playing their first tournament. I made a bet and was called on the flop. I made a bet on the turn and was called but when the other guy called he turned over his pocket aces. I was drawing dead and happy he showed me so I could fold. The dealer called the boss over and they declared his hand dead and awarded me the pot because he showed his cards before the betting was done.