For those of you saying the actor should have checked the firearm and made sure it was empty, I think you are misunderstanding the issue. From the reporting I've read, the gun in question was a Colt Single Action revolver. The big issue with revolvers is you can see into the cylinder and tell whether the gun is loaded or not. It's one of the first things I look for in any scene that has a revolver that faces the camera - if the cylinders are empty the scene loses all credibility. So unlike a firearm that uses a magazine where the cartridges are not visible, revolvers require dummy rounds to look realistic. In revolvers wax bullets (or some similar material) are often used if the open cylinder will be visible during firing. Oftentimes the cartridges will be loaded with just a primer, which is enough to fire the wax bullet. The wax can still dangerous but under the vast majority of circumstances not lethal. But they can be made to look identical to normal cartridges, which is the point.
So to say that the actor should have checked and made sure the gun was empty does not apply here. Actors and everyone else on the set rely on the armorer to make sure guns, whether prop or real, are safe for the scene in which they are to be used. Discharging a firearm directly at the camera is very common in movies. And think of the thousands of movie scenes that show an actor loading rounds into a magazine and then into a firearm and cocking it to make sure it is loaded. By the logic of making sure the gun should be unloaded such scenes could never have been filmed.
It's been stated in the press that the scene being filmed had the actor shooting directly at the camera. So the actor did exactly what he was supposed to do. If you are blaming the actor you might as well blame the screen writer for writing that action.
In my mind, the real fault lies with the armorer and the AD who picked up the firearm and handed it to the actor. The armorer's primary responsibility is safety. The AD should have verified with the armorer that the gun was in fact a 'cold gun' before passing it along.
There have been deadly firearms accidents on movies set before, and there will likely be again. I don't mean to sound cavalier but the same is true regarding car stunts - no matter how many stunt actors have been killed or seriously injured filming car chases and crashes, they continue to be filmed as 'practical' effects. (Real cars and drivers, not CGI.) No matter how good CGI is, for some shots practical effects are just easier, faster, more realistic, etc. Unless firearms are specifically banned from sets, they will continue to be used.
Tony
PS: After reading through the Wikipedia list of film and TV accidents, a much more obvious conclusion would be to ban helicopters from being used to film movies:
https://en.wikipedia.org/wiki/List_of_film_and_television_accidents