These are the two people who are actually responsible for what happened to Halyna Hutchins.
Not many more details here, but we have a very inexperience armorer (with a decent pedigree), Hannah Gutierrez, and an Assistant Director, David Hall, who seems to have been the one who actually gave the gun to Baldwin, telling him it was "cold".
Just based on this, it seems that 3 guns were left on a cart outside of Gutierrez' supervision. Right away, that's a big fail. But worse, Hall should never have even touched a single one of those guns and he sure as hell should not have told Baldwin that it was clear.
However... The biggest question of all still remains: Why was there a live round on set at all?
At what point did one of these guns get loaded with an actual bullet? Who did it? For what reason?
I've heard some rumors, btw... Not sure if they're true yet, but it's also possible that people took the guns offsite and were shooting them.
Either way, the fact that the armorer didn't actually clear the weapons, and even worse that the AD seems to have taken one off a tray... Huge issues.
Baldwin isn't the expert here. Firearms on set often have blanks and dummy loads that look like real bullets, but which actually aren't. He can't -- and isn't -- expected to know the difference. He's also not expected to obey normal rules you'd apply to any gun range because (somewhat obviously) he actually has to portray characters who point guns at and shoot people.
Baldwin could have checked and seen what appeared to him to be the blanks that were supposed to be in the gun.
He could have checked and saw nothing, when in fact the scene was supposed to feature blanks or dummy loads, in which case the scene would have to be redone.
His job is to act, not to oversee the condition of the firearms. That's the armorer's job.
You're asking Baldwin to know the difference between a dummy round (which often looks exactly like a real bullet) and a live round. You're asking him to break his concentration and step out of character right before the cameras are about to roll on a scene to pull out a magazine or open up the cylinder on a revolver, pull out all the bullets and inspect them to see if they're actually blanks instead of real bullets.
I don't know how else to explain this to people, but that's not his job, and it would be a disaster if you made it the actors' jobs to do what you're suggesting that they do.
Division of labor in this regard is a fact and it's an essential one. Yes, actors should be expected not to engage in any kind of horseplay with guns on set no matter what. They should be expected to act professionally and only use guns for what they're meant to be used for in the scene.
But there's a reason that filmmakers hire armorers and why the standard protocol is for those specific individuals to be in charge of every aspect of weapons on set.
I used this example before, but there's a ton of other dangerous things you could hand to an actor that they need to trust the team to give them the right thing. There are plenty of instances where actors and stunt-people fight with knives or swords. Typically, they do so with swords that are not sharp, have rounded points, or which are not even made of metal at all but look and feel comparable to the real thing. But props teams also have real swords on set to use as the "hero" -- the weapon that gets all the closeups and fine detail shots. Those are just real knives and swords.
You can see how realistic some of the ones they made for Rambo looked, and that was a comparatively low budget movie from 50 years ago.
If the armorer handed Stallone the wrong knife, we'd hope that he'd recognize the difference between a sharp and dangerous one vs. the safer version meant to be used for the fight sequence, but his job in that moment is to remember fight choreography, remember his lines, hit his marks, and dance with the stunt team to make things look as real as possible. His job is not to second guess the other professionals he's working with or be an expert in props.
That's the problem. Unless Baldwin was doing something that was actually negligent (ie. if he picked up a gun he wasn't told to, or he was playing around with it for no reason, etc.), then he's not the one you need to focus your attention on here.