Sounds like a fairly routine kill to me. The deer dropped because of the shoulder wound. It was unable to regain it's feet because of the blood pressure loss. I've never been fortunate or skilled enough to drop and kill one on the spot like that, however I've "spined" a few. It's frustrating when you put another arrow in them and there's no reaction whatsoever. Once or twice I've gotten excited and emtied my quiver on a spined deer. Times you look back on and laugh.