Runaway car doing 90? Was the throttle stuck too? And, couldn't get it into neutral? All while headed down a 30% grade, with a tail wind? You could of hurt or killed someone. Maybe you need to keep a closer watch on your vehicles safety equipment.
Both parties get a photo op with the deer, split the meat, and treat the mount like the Stanley Cup. You each get it for a year on an alternating schedule.
I've been using 1 for at least the last 15 years. Dead on at 20 yards and in. Anything further just make minor adjustments. Practice enough and you'll have it all figured out.
Put a lien on his house. It's easy to do and you don't need to show any sort of proof to do it. And, it's perfectly legal. He'll go to sell one day and have a major headache.