There are professional weapons handlers in the prop department to make sure all firearms used are safe.
Until there isn''t.
When Brandon Scott Lee died, he was shot in the abdomen with a .44. The bullet lodged in his spine It was during the final weeks of filming, and supposedly the weapons expert had already left. They still needed to film the scene where Lee's character was murdered, and someone else loaded the gun with a live round.
There was a theory that part of a "dummy bullet" was lodged in the barrel, and a blank turned it into a projectile. Dummy bullets have no powder or primer, and are used for close-ups when they want it to appear as if the gun is loaded with real ammo. Then the dummy bullets are replaced with blanks for any shooting sequences. Experts have said that's highly unlikely if they were using well-made dummies. But, since the last weeks were hurried and the expert wasn't there, it's possible someone tried to create dummies and didn't do a good job -- meaning there could have been a "squib" type bullet head in the barrel if the dummy bullet separated.
There's no direct evidence of a squibbed dummy bullet, and I imagine they would have examined the firearm and determined if the round fired was a blank or not, so why this theory still exists is puzzling to me. I could see someone making up a theory to avoid being blamed for loading the live round.
This accident will likely follow a similar path. Lots of questions, incomplete and inconsistent answers, but no definite conclusions. Baldwin is rich, famous, and a woke-sounding Democrat. Somebody will shield him (ala Jussie and Kamala).