Sometimes I find it hypocritical that so many people are crying foul. Unless you are a vegetarian or belong to a vegetarian denominator, I don't think you get a vote on judging this marine.
How does being an omnivore have anything to do with cruelty for cruelties sake? That's all this is about. The puppy could not have harmed the marine, but the marine decided to kill it anyway, and in a very cruel way.
Anyone who doesn't think cruelty to animals eventually translates to just plain cruelty to anything or anyone is simply hiding their head in the sand. Most violent criminals have no regard for any life, animal or human.