Close to a prima facia case?... I'm sorry but nope. First off The police are under no requierment to allow an adversary to get off the first shot. If the subject pointed a firearm in the general direction of the police... he's probably going to get shot.
Could an officer have heard another officers firearm going off, and believed the subject was fireing at him? Then after debriefing realize that he was mistaken?... It happens. He's not changing his story... He's correcting his misconception. I dont know thats what happened but it's a lot more likely than the police murdered anyone.
As I've said before... I'm probably one of the harshest critics of todays police tactics. But in this case I dont see any real fault. I feel even stronger that they were justified after watching the vidio.
You cant point guns at the police. Even if it is on safety. Well you can but expect sad results.