A lot of writers and movie people don't know much about real-world things (like fire, electricity, basic physics, how business works, guns, airplanes, cars, etc.).
One of my favorites:
Person is pointing semi-auto handgun at someone, threatening to shoot if he doesn't do what he's told. The person doesn't give in, and the would-be shooter says something like, "OK, that's it!" and then racks the slide.