Brilliant post. It wasn't necessary? So he shoots the guy in the leg, guy falls to the ground and takes out a handgun he had hidden in his pants and shoots the old man in the head, killing him.
i guess if your a fightful, scared, weak, impatient, rash-decision-making, old man with a history of being in the army and having killed people before.. then sure you might feel it necessary to shoot a man for breaking into your house.
me on the other hand, i dont feel it would ever be necessary to kill someone unless it was OBVIOUS that they were about to kill someone else and the only way to prevent it would be to kill them. This scenario really doesnt fit that one. In any case, celebrating a death is always misguided, no matter how practical the necessity of causing the death may have been.