Fishing Cabin, with all due respect, that's a horrible analogy.
Moises Zambrana, or the guy who was looking at the Ruger 9mm, (not clear who was actually handling it when it fired) was grossly negligent in handling a gun, with a chambered round, in a public and populated area.
OTOH, the shooter in this thread had just been attacked by a gang, and was being man-handled by a person whom he had some legitimate reason to suspect might not be a cop.
Those are grossly different.
Zambrana and friend were criminally negligent, at the least. I wouldn't want the DA to go for maximum charges or penalties, but an assault or (hopefully it won't come to this) negligent homicide charge would be appropriate.
In the case in this thread, assuming the officer used the force described, and if all else is as reported, I'd find Not Guilty as a juror. The standard is what a reasonable person, with the same knowledge as the defendant, would do in the same situation. I could easily see myself thinking "fake cop," and fighting for my life in that same situation, based on the combination of the gang setup, the non-police car, the tattoos, and the rough handling.
Apples and oranges between that and Zambrana.