"Reckless conduct" is any type of conduct wherein the defendant knew or should have known that their actions would cause harm to another person.
Reaching into one's pocket isn't reckless, nor would it have been even if he had dropped the firearm. Nor was his accidental discharge of the pistol as reckless conduct requires a deliberate action. The law recognizes that not all accidental conduct is reckless.
Nothing the officer did was done with deliberate disregard for the safety of others... so.. not reckless as the District Attorney interpreted the law.
Now, if you DO want to see a travesty of justice and a District Attorney bending the law, all you have to do is go to the case of the
Los Angeles County Sheriff's Deputy who wasn't charged with anything after he left his travel lane and ran over a bicyclist, killing him. The DA in that case deliberately mis-charged the Deputy so that he wouldn't be tried in court.