Hi- I also used to be an on-set armourer’s assistant in Canada. We assembled and counted every blank and checked each firearm between shots, and never let anyone handle the firearms unless it was for the scene.
The reason you have blanks in the gun (why they are necessary) is because it just looks better than digital composite, and lower budget films can usually afford blanks more than they can the cost of post-production effects. There’s even some artistry in creating the blanks: flash powers can have different colour effects and you can control the amount of muzzle flash by how much powder you pack into the blank.
We don’t know the details of this situation yet, but a “point at lens” shot with a blank is common and likely the culprit. When we did it, we made sure that there was a sheet of lexan between the camera and sound blankets covering things. What I currently think (with absolutely no proof, mind you… pure speculation) is that it may have been a shotgun that had some blockage in the barrels and half-blanks, because it hit two people and caused enough injury to be fatal/almost fatal.
When you train actors to use these firearms, you do have to remind them that it’s still dangerous- and even a blank will kill someone at point-blank range. That’s why I always cringe when I see a gun held up to another actor’s head… someone who is unfamiliar with firearms but lost in the scene won’t have the best trigger discipline.