This was an Old West, single action firearm like a Colt Peacemaker or a Winchester rifle. So WHY ON EARTH did he fire 2
The movie is a Western, so all weapons would be Wild West guns. Single action firearms that must be cocked for each shot. With the Colt revolver, you pull back the hammer with your thumb. With the Winchester rifle, you work the lever. It's not like a modern semi-automatic where all you need to do is pull the trigger.
If you fire one supposed blank and a crew member falls to the ground bleeding, why the hell would you cock and fire AGAIN?
Sounds intentional to me. Alec is a murderer.