the piece he drilled was the cup, they would have had to have gone through it then took the anvil out.
then drilled the flash hole.
I'm assuming they went in and hit the anvil, wedged the bit to the side some, and snap.
back in the older olden days you could buy little kits for shot shells to reload the primer as well as the case.
I used to make them for a local store here. Best way to do it is leave the primer in. Then run the shell into the crimp starter then in the final crimp. Then all you have to do is slide the light bulb right into the crimped end. One of my side jobs to make more $$$$ for reloading supplies.Someone was converting the hulls into decorative globes for Christmas string lights when they broke a bit. Seriously.