I don't get it. The guy was drunk, he was walking/running away and he gets shot in the back. By any standard that's unacceptable. The police had his wallet in their possession, they knew where he lived. They could have just set up an ambush to take him down when he got home. He would have never expected it.
I only say it's a tough call on how to charge the cops because I wasn't there. I wasn't in that situation. The perp already fired at the LEO's with a Taser. That is considered a weapon.
Why the dude didn't just go to jail for the night and sleep it off is unknown. Up until the point he was going to be cuffed, he was going with the program. Had he just remained quiet, he probably would have just gone home if he had someone to pick him up.
A simple, 'Yes, Sir, No, Sir', even if you are in the wrong will save you a shitload of grief. The Courtroom is the place for controversy, not the street.