Alec Baldwin was using a real gun loaded with a real bullet to practice his "quick draw" technique when he fatally shot his own female employee.
The gun was a fully functioning and unmodified historic 45 caliber colt long revolver.
NYT: Rust-shooting-investigation Some prop guns are fake plastic guns, or they may be real guns modified so they can't fire or they might be modified so they can only take and fire blank rounds.
In Baldwin's case, he was using a fully functioning and completely unmodified historic 45 caliber colt long revolver loaded with at least one live round.
The bullet that killed the photographer was a 45 caliber lead bullet.
In fact, some members of the film crew had been using this very real gun to plink away at very real beer cans with very real live rounds shortly before the very real fatal shooting.
So everyone knew this was a real gun and everyone knew it was quite capable of firing live rounds.
Ironically, Baldwin himself is a well-known advocate for gun control.
And yet Baldwin violated just about every rule of gun safety there is in the course of his own movie production....and unfortunately a woman died because of Baldwin's carelessness with firearms.
Bang!