I wonder whether the revolver was chambered for
metallic cartridges, or was a
muzzleloader? All the film synopsis says is "Western" which - depending on the timefame - could involve either.
Many film prop handguns have been converted to fire multi-calibre blanks, though ones specific to calibre, e.g. .38 Special, .45 "Long" Colt, .38-40 etc. - are available.
To kill one person and injure a second implies a projectile, whereas most blanks are simply powder charges, topped with a paper or wax wad, with the end of the cartridge case crimped to retain the propellant:
I find it very difficult to believe that a fragment of such wadding could do such damage to two people.
The involvement of Alec Baldwin raises red flags for me, as he does not have a good reputation regarding temperament and stability.
The investigation will doubtless be thorough. Until its conclusions...
maximus otter