The irony of that linked article, younggunz4life, is that the accompanying picture shows a Browning Hi-Power, a gun that (unmodified) has a magazine disconnect safety. Odds are that is not the type of gun the guy in that article was using (shot himself after removing the magazine from whatever gun he had).
The article didn't really describe the environment in which that shooter was performing his demonstration.
In the case under discussion in this thread, though, Zambrana was manipulating a gun in an occupied building.
While fiddletown is correct, in that a court will decide if it was simple negligence or something more culpable, my opinion is that the closest traffic parallel would be a guy showing off a car he was trying to sell by gunning the engine and speeding in a residential neighborhood.
To me, neither would be "simple negligence," if injury or death to a bystander were to occur.
I think the thing that may help Zambrana most is that the victim's family seem to want to treat this as an unfortunate accident. I would not fault the prosecutor for honoring the family's wishes, and taking a more compassionate approach.
But I also wouldn't fault him if he went for negligent homicide or involuntary manslaughter.