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Investigators with the Santa Fe County Sheriff’s Office confirmed Thursday that one person was killed and another injured after a “prop firearm” was discharged by Alec Baldwin on the New Mexico set of his film “Rust.”

Halyna Hutchins, the film’s director of photography, was pronounced dead by medical personnel at University of New Mexico Hospital. Joel Souza, the film’s director, was transported to a separate medical facility for treatment.

The circumstances surrounding the incident are still under investigation, according to police. But prop guns are extremely common in the film industry, and their use is strictly regulated.

The term “prop gun” or “prop firearm” can be used to describe a few different types of guns, including non-firing synthetic rifles or rubber lookalikes. In many cases, though, a prop gun may be a functional gun loaded with blanks in order to recreate the muzzle flash, or the sound or feel, of a real gun discharging.

Such prop guns are not designed to fire anything but blanks, but can still be fatal if handled incorrectly, or at close range, due to the ejection of any wadding or plugging used to hold the gunpowder charges in place.

“A blank is a round, but without a projectile, so there’s still a lot of force in there, there’s still a lot of pressure and can be dangerous if not used safety,” Sam Dormer, an armory coordinator and supervisor who worked on such films as “F9: The Fast Saga” and “Wonder Woman 1984,” told the Associated Press.

Brandon Lee. seen here in 1986, was killed during the filming of “The Crow” in 1993. (AP Photo/Lacy Atkins, File)

The mishandling of prop guns, and sometimes just the force of a blank discharging, has previously caused the deaths of at least two other actors over the last several decades, most notably Brandon Lee, who died on the set of “The Crow” in 1993.

Lee, the son of martial artist and actor Bruce Lee, was killed when a prop gun loaded with blanks was fired in his direction during filming, but it wasn’t the stuffing or plug that struck him. When the blank was fired, the gun dislodged an obstruction that had previously gotten stuck inside the barrel of the revolver — an obstruction that was not removed before the gun was reloaded with blanks. Lee was 28 years old.

Another notable accident involved 26-year-old actor Jon-Erik Hexum, who was rushed to the hospital after playing with a prop gun that he believed to be harmless, placing it up against his temple during a break in the filming of the 1984 series “Cover Up.” His skull was fractured and he was later pronounced brain-dead, dying less than a week later.

Preventing such accidents is the job of a film’s safety crews and armorers, according to Dormer.

“There are lots of checks in place. So for instance, with the Brandon Lee incident there was an obstruction in the barrel, which came out once the blank was put behind it. And nowadays, all weapons are checked, the barrel is checked before any blanks are put into the weapon,” he told the AP. Dormer added that the actors, too, are trained to use the prop weapons.

“The blanks themselves are never loaded until the very last minute when all crew is in position so the armorer knows exactly where every member of the crew is, so that no one’s walking through any danger areas the armorer has set up,” he said.

Steven Hall, the director of photography for films including “Thor: The Dark World” and “Assassin’s Creed,” also told the outlet that safety protocols on film sets are usually “very strict and very well adhered to,” but acknowledged that accidents are more likely to happen during rushed productions.

“I’m not saying for a moment that this could be the reason behind this, but it’s certainly something that anybody like me that works in film and TV on a day-to-day basis has certainly experienced many, many times,” Hall told AP. “It could be the fact that safety protocols were, shall we say, relaxed for a moment simply because the light was going. Or, as I say, there was another extraneous reason why things had to be speeded up.”

Prop guns used in film or television production, such as the one seen here at a film armory in France, can refer to real firearms designed to be loaded with blanks, or non-firing lookalikes made from plastics or rubber. (Thomas Samson/AFP via Getty Images)

Reports also emerged on Friday morning that the prop gun on the set of “Rust” had contained a live round rather than a blank, according to an internal email from a union representing prop masters, which was cited by IndieWire. If so, Hall explained that he has “certainly” known of productions that used live rounds to test the revolvers used during filming, to make sure “it isn’t going to blow up or explode in the actor’s hands.”

“So there is a theory, of course, and I’ve just read a theory that maybe a live round was left in the gun,” Hall said. “I mean, it would be inconceivable to me that that could happen, but it is another possibility, sadly.”

The accident has also spurred discussion over the use of firearms as prop guns, and whether film and TV productions should move toward a safer alternative.

Dormer, for one, believes it’s only a matter of time before the industry begins embracing other options, including gas-powered prop firearms that behave like real guns.

“And, the film industry will be moving that way very soon, I feel,” Dormer said.

The Associated Press contributed to this report.