To begin with, one's thoughts should be with the family of the young women who was tragically killed.
While it may be easy to pile on to the "name", especially when his political views, celebrity image (good and bad) and past comments makes him a ready target, let's remember that this was a movie set and the same rules and protocols of weapons handling that
most many of us (hopefully) take as second nature would not be routine for the talent as much as it should. Even those of us more comfortable with firearms were regularly reinforced with training in safety precautions (along with IAs) each time that we used live rounds (i.e. range briefing). Still, there were "accidents" far too often.
Now, I do recall several films featuring this actor in which firearms use was central to the plot and he very successfully "pretended" (this is what acting is) to have a facility with firearms. However, there are a whole lot of people behind the camera whose jobs are to make him look like he knows what he is doing. But, just as for those who carry weapons as part of their job, familiarity can breed an over-developed sense of everything's alright.
There have been many articles popping up about movie set firearms protocol in the past few hours
and
Cinematographer Halyna Hutchins died Thursday after Alec Baldwin fired a loaded weapon that was handed to him by an assistant director who mistakenly believed it was safe to use on the New Mexico set of “Rust.”
apnews.com
And some from well before this tragic incident
Filming With Firearms - The American Society of Cinematographers (OldSolduer, perhaps your FAC instructor?)
and
New York's #1 provider of LIVE blank-fire firearms, Exotic Weapons for TV, Film & Print
www.moviegunservices.com