> What did you expect them to use? <
A realistic fake gun. One that can go boom, but absolutely cannot fire any projectiles.
You would have to custom make such a thing, and it would likely cost more than just an ordinary gun.
That’s not how it works. Guns are just hunks of mechanical metal. What matters is what’s loaded. Live rounds or blank rounds or, apparently, lazy prop people who just turn live rounds into non-firing rounds but still have functional primers.