Mucking hand at showdown

[keith1174]

This past weekend we had a situation in our game. 2 players to the river and the player 1 bet and was called by player 2. Player 1 immediately mucked his cards but they did not hit the dead cards on the table. Player 1 asked player 2 what you have 2 pair. Player 2 refused to show his cards and player 1 was upset because no hand was shown to win the pot. Eventually he showed A high. Player 1 insisted that p2 had to show cards because p1 mucked his cards. Is there any type of ruling that says they have to show their cards because the other player mucked his cards. In my opinion the mucked hand is dead and he forfeited the hand, so it is over. Is that correct?