Don't sweat it. What you did was what you should have done. I had the same thing happen to me back in 02. I had a father and his two sons hunting in a triangle 100yrds all around me. We talked going in at 5am and we all explained where we were going to be. Well by 7am the kid shot a small buck with buck shot twice breaking what I think was 3 legs! Ever see a deer run on three broken legs? Or for better words run on one good leg? It came 30yrds from me after being shot flopping then driving itself forward with one leg. It stopped and laid down making that bahhhh sound so after about 3 minutes of hearing that I got down and at point blank range put it out of its misery not at all thinking it was anything but. I heard the group trying to track the deer so I approached them and showed them were it was. The father flipped it over looking for any sign of a mortal pellet wound then looked at me and said congratulations and told his boy it was rightfully my deer. I tried to give it to the boy but I guess his dad was trying to teach him a lesson.