Several comments above say that Baldwin should have checked the gun himself when it was handed to him.
In "real life," personally checking whether or not a gun is loaded is correct procedure. But not on a movie set. Many actors are not shooters in real life and are not familiar guns. I overheard several actors say they were a little nervous because they had never even touched a gun before. Having someone who doesn't know anything about guns check them for safety is a recipe for disaster.
Gun safety on set is the responsibility of the prop master or the armorer. They are responsible for the guns themselves, and also for insuring that the actors know how to handle them. For example, one young actress who had never touched a gun before had to grab a shotgun and kill the bad guy. So they took her off set somewhere safe and taught her how to handle it and let her shoot it a few times so that, on camera, she looked like she knew what she was doing. Which she really didn't.
News reports indicate that the gun was handed to Baldwin by an assistant director. That is a safety violation. Why was anyone other than the the armorer (or an assistant armorer) dealing with guns? News reports also indicate that this assistant director told Baldwin that the gun was safe, which it obviously wasn't. In all my years on set, I never saw anyone other than a prop master or armorer give a gun to an actor.
As I said above (post #17) camera crews tend to extremely conscious of gun safety because, aside from the actors, we are closer to the action than anyone else, and therefore most in danger should anything go wrong. And it's not only when things go wrong. When the actors shoot toward the camera, they are shooting right at us, and often at close range. As an assistant, standing right beside the camera, I personally have had guns (mostly 9mm and .38, but also shotguns and once, for an extra level of excitement, twin .50 cal machine guns) fired right in my face hundreds of times. So, I am not surprised at all that the camera crew had quit over previous "misfires."
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VICTOR - -
Yes, The International Alliance of Theatrical Stage Employees did just renew their contract. Local 600, the International Photographers Guild, is part of the IA. The camera crew members who quit are memberS of that local.
Regarding James Cagney's statement that real guns were used in old movies, well, don't believe everything you read.