[thenrie]

It was probably against the law for the deputy to shoot the deer. Game animals belong to the state and are under state regulation (not the county). If you shoot a deer, even if you hit it with a car, out of season and without a hunting permit, or if you shoot "onto, from, or across any roadway", you are in violation of state game laws in most states and can be cited. You could also be cited for shooting a firearm in close proximity to an inhabited building. What you are supposed to do if you hit a deer is to call the state game and fish department or county animal control and have them handle it. A deputy sheriff can shoot legally just about anywhere, but he has no authority to kill a game animal without a hunting license and in the proper season.

Reality, on the other hand, is that almost certainly nobody is going to prosecute a deputy sheriff for putting a deer out of its misery. They make those laws and enforce them because if they didn't, there are folks who would poach deer and bear from roadways and claim they had hit it with their car and were just putting it down.