That's because death comes with the loss of blood to the brain.
Hunters know a shot to the heart/lungs of a deer will allow the deer to make up to a hundred yards running with their heart blown out the other side because of the speed they run before the brain realizes that it has lost blood supply and dies.
A shot to the central nervous system is the only thing that brings instant death and LEO/military know that.
A gun fight isn't a target shoot where one can put a round into the perfect spot. It's a major snafu where everybody is looking for cover and moving while shooting unlike what is seen on TV.
You shoot until the threat is no longer a threat. I don't see anything in this case other than an overzealous prosecutor looking to make a name.
I suspect that prater is going to make a run for state AG.