While I deeply regret this happening, I sincerely hope that you use your video and information about this occurance with different animal organizations. You brought up several VERY good points. One being that this issue is chronic nationwide. Video feed is being passed around on FB about a female runaway dog that was WAGGING HER TAIL at officers, begging to get in their good graces, and one officer puts his foot on her neck, TAIL STILL WAGGING, & He point blank shoots her in the head. NO AGRESSION THERE. So I'd be sure to ask for proof. Many officers now wear recording devices on their person. Perhaps PETA should be enlisted, or at the very least contacted. YOU can make your dog's death mean something perhaps. I, for one, would be on the band Wagon to help.
PLEASE don't lower yourself to slanderous comments by ignorant people. Responding just makes them feel more powerful. Something they lack in their lives.