In wake of Alec Baldwin firing a prop gun Thursday on the set of his movie Rust, killing cinematographer Halyna Hutchins and injuring director Joel Souza, The Wrap's Ross A. Lincoln explains how a prop gun can be deadly. The union IATSE says the gun contained a "live single round." "As is often the case after such events, there’s a lot of confusion about what, exactly happened," says Lincoln. "If the gun was filled with blanks, how on earth could someone be killed? How can a 'prop' gun be deadly. Was a crime committed? We’ll attempt to answer those questions here. Of course, we must also stress that the details of the tragedy on the Rust set are far from complete and it will be days, if not weeks before, we know the full story. First, it’s important to understand what the term 'prop gun' means in this context. People tend to assume it refers to non-functional weapons of the sort used in theatrical performances, or toy guns that fire caps to produce smoke. And while it’s true that those are also prop guns, the term also applies to real guns that are used as props. The reason a production would use a real gun is simple: Verisimilitude. As firearms instructor Dave Brown wrote for American Cinematographer magazine in 2019, real firearms add authenticity to close-up shots in particular. Anyone who’s ever held a gun can confirm that a real gun looks, weighs and handles different from an inert prop. But, Brown noted, they also require experts on set to make sure they’re properly handled at all times. That’s because a gun is still a gun, regardless of what’s in it. And that brings us to how a gun loaded with blanks can kill someone. The term 'blank’ is a shorthand version of the full term, blank cartridge. Notice I said cartridge and not bullet. A cartridge is a unit of ammunition fed into the barrel of a gun comprised of several parts: The casing (sometimes called a shell); propellant material (gunpowder) inside the shell; a primer on the bottom of the cartridge; and at the tip of the cartridge, the actual projectile (bullet) itself."