I would not feed it to my snake. Might be something wrong with it. Shelby is correct also, if there were 2 males, the other male would have killed off the 2nd (weaker, smaller, etc) for mating rights. But, that dont explain why they were "eating" it as you say they were, cause normally, one will be killed off, often wounded as you said (face torn off, etc). I kinda think it may have been a combination of the fact, the one that was killed was a male, and they also may have not had enough food, or felt they did not have enough. Mice are kinda strange like that. But I have seen rats do just that when there is not enough of food to go around.