No snarkieness taken.
It could have been that he thought he was reaching for a taser. It would not be the first time that has happened. There was a Chicago Sergeant who did the same thing a few years ago. And like this case, it was after recently after her department recieved tasers.
I cant imagine that he pulled out his weapon in that situation unless he saw something that we did not see on the tape. If he indeed intended to pull out his weapon, then he screwed up by not indexing (keeping his finger out of the trigger well) unless and until he meant to fire. In that case, I can understand a charge of negligiant homicide but not murder.
If he meant to pull out a taser, and accidentally pulled out his weapon, I am at a loss as to whether he should be charged.
Keep in mind, this former officer has a baby that is about two weeks old. That might be the only thing keeping him from eating his gun. You can tell from his reaction right after the shot, that he knew he screwed up.
This is a tragedy for everyone involved.
I have seen armed policemen and it seems that the taser is on one side and the firearm is on the other. Furthermore, from previous reports, it seems that this guy had it taser out previously. I have no doubt that this case will be pled down to a lesser charge; that seems to be what happens generally speaking. However, he refused to be interviewed by the department or participate in the investigation. No doubt he probably 'lawyered up', which clearly he should have done immediately. Perhaps on advice of counsel, he was advised to resign and not cooperate, I don't know. But if we are to believe our "lying eyes", it looks like an execution. It looked like an execution to the witnesses, and he better have a great lawyer. The truth could be different, and while everyone has a presumption of innocence, he has a tough row to hoe.

It looked to me like the officer was stunned by what he had just done.