There are lots of possibilities. The scene could have call him just to point the gun at the camera and cock the hammer, or pull the trigger and cut right before the flash. Or, pull the trigger and add CGI.
Since this event I’ve been watching carefully shows where they have shootings, and watch how they frame and cut it. It’s interesting.
CGI for things like gun flashes is cheap and easy.
. I don’t know how modern westerns compare to older TV stuff, technically, but I saw a lot of shooting on MeTV, today and don’t recall any flash. I’ll have to pay more attention.