But in terms of criminal charges, he's got a "professional" on set whose primary responsibility was to ensure that there was nothing that would propel a bullet out of the barrel. And not where one is removing a firearm that was stored, but supposedly checked minutes before the scene.
Yep, and that is one explanation given by the production company which will be considered. But it's only one factoid out of thousands that could influence the prosecutor's decision.
As the sheriff explained in the press conference, they impounded more than 600 pieces of evidence at the scene. About 500 of those were pieces of ammunition of various types (blanks, fakes, and real stuff).
They impounded another 100+ pieces of evidence besides the ammo, each of which will have to be examined to determine what, if anything, they tell investigators. We don't know what those are, with the exception of a very few obvious items
There are 90 potential witnesses who were present on the set when the shooting happened. Each of those will be interviewed, many of them more than once, and some probably several times. We don't know what they know, saw, or will say.
We also don't know the details of what was happening
during the actual shooting. All we know is some really basic (and
unconfirmed) information saying that they were doing a walkthrough of a scene because they were having a problem with the lighting and shadows. That tells us almost nothing
This investigation is going to take weeks, and a lot of what we know right now will turn out to be trivial or downright irrelevant.