Maybe they and the police deserve each other.
All I can say is that if I carried both a pistol and a taser and used the pistol “by mistake” to shoot a fleeing or fallen person, I probably wouldn’t have gotten the benefit of the doubt.
What if you had the guy on the ground prone, hands behind his back (cuffed IIRC), and shot him in the back? Do you think your sentence would be higher?
In most states, a private citizen has a right to use deadly force in an attempt to arrest a fleeing felon; even more leeway than a cop.