Hi Jorge,
Killing a live hand is not in the best interests of a tournament, the objective of any tournament is to go from total entries to 1 player within a set timescale, to kill a hand, goes against this basic objective, the player who exposes his cards has a disadvantage against the other player also, as he has given that information away for free. The TDA policy is to complete the hand then punish, for example two players make an agreement to check down an all-in player, with is highly unethical, you would allow the hand to complete them disqualify or severely penalise the players once the hand is complete.
In your scenario, if it was at my tables, the player intentionally exposes their cards with malice and the player won the hand, I would penalise them with an orbit amount that penalises them for more than they won in the hand, if they loose the hand it would likely be one round, if they exposes their cards unintentionally or without malice then the penalty would be lighter, likely 1 hand - 1 orbit.
The most important factor you must adopt however is the TDA principle that killing a hand which is live is not in the best interests of tournament play. I do know there are several rulesets which are not in keeping with this, which are fair to be said, behind the times. I only ever generally announce hands that have already been killed by the dealer or those with improper starting hands etc, I can't remember the last time I ever killed a hand which was proper and in custody of the player. Announcing at the start of the Tournament that a player will have a dead hand is not compaticle with the TDA. Also stating that a player who exposes their hand can only call is not workable either, they should have all options available (check, call, raise, fold) as again binding that player to passive action is not in the best interests of tournament play.
Regards
Stuart