Lukeo83,
Sorry but, if the player were initiating the bet, he would be all-in. because he was not the original bettor, it's a call. It has some similarities to a player tossing 2 5K chips into the pot on the turn when under the gun...he has just bet 10K. The same player, facing a 12K bet and tossing 2 10K chips into the pot has only called.