It’s been nearly three weeks since "Rust" cinematographer Halyna Hutchins died in an on-set shooting involving actor Alec Baldwin that also left director Joel Souza hospitalized.

It remains unclear how and why a  suspected real bullet made it into the prop gun – believed to be a F.LLI Pietta Long Colt .45 Revolver – which Baldwin had allegedly been handed by a crew member moments earlier, according to the sheriff of Santa Fe, New Mexico.

Investigators say they recovered hundreds of rounds from the set, including dummies, blanks and real bullets. They said all of the individuals who handled the gun on Oct. 21 are cooperating and have not announced any criminal charges.

Halyna Hutchins Rust

PARK CITY, UT - JANUARY 28:  Halyna Hutchins attends the SAGindie Sundance Filmmakers Reception at Cafe Terigo on January 28, 2019 in Park City, Utah. (Photo by Fred Hayes/Getty Images for SAGindie)

‘RUST’ MOVIE SHOOTING: DEPUTIES CONFISCATE WEAPONS, AMMO FROM SET

Phelim McAleer, an independent filmmaker who has worked with on-set armorers before, said there are strict union guidelines for handling firearms that don’t always get followed closely.

A so-called live round on a movie set is usually defined as "any shot that has combustion and that includes a blank, so every set that fires a blank fires a ‘live’ round," he told Fox News Digital from Serbia, where he is filming a forthcoming Hunter Biden biopic.

"However an actual bullet on a set, never mind in a gun, that is completely mental and unprecedented." 

— Phelim McAleer, independent filmmaker 

The woman in charge of the film’s firearms, armorer Hannah Gutierrez Reed, told detectives last week that there should not have been any real bullets in the area whatsoever, according to the warrants. 

Alec Baldwin spoke with reporters about the deadly on-set shooting on the movie 'Rust.' (Fox News Digital)

LAWYER FOR ‘RUST’ ASSISTANT DIRECTOR DAVE HALLS REFUSES TO ANSWER WHETHER HE HANDED GUN TO ALEC BALDWIN

"Bullets should not be on set – or in firearms that will later be fired, because they can get jammed in the barrel and pushed out by a blank," McAleer said.

That’s what happened in the 1993 filming of "The Crow" – launching a projectile that fatally struck actor Brandon Lee, the son of Bruce Lee, in the spine.

McAleer said that while there are supposed to be union-approved safety protocols in set, sometimes enforcement is lax. On top of that, firearms experts and filmmakers have told Fox News Digital that a weapon should never be pointed at another person on set to begin with. 

SANTA FE, NEW MEXICO - OCTOBER 27: Santa Fe County Sheriff Adan Mendoza updates media on deadly ‘Rust’ movie shooting. (Photo by Sam Wasson/Getty Images) ( )

"It’s called movie magic for a reason," McAleer said. "Even if the script says point it at a person, we have tricks to avoid direct pointing."

HALYNA HUTCHINS’ DEATH ON ‘RUST’ SET WAS ‘COMPLETELY PREVENTABLE,’ ARMORERS SAY: ‘SAFETY WAS NOT PRIORITIZED’

The Santa Fe Sheriff’s Department on Tuesday said its investigation into the incident remained ongoing and that it had no new developments to report.

Other indie filmmakers told Fox News Digital that they go even further to ensure safety on set, using Airsoft weapons and adding in muzzle flash and sound in post-production.

"Even if a gun isn't a real gun, even if it's an Airsoft gun, you're supposed to check it," said Corey Asraf, who recently directed "Let Me Make You a Martyr" starring Marilyn Manson. "You're supposed to treat it like it's a real gun. That's the procedure."

‘RUST’ ARMORER HANNAH GUTIERREZ REED BREAKS SILENCE ON HALYNA HUTCHINS TRAGEDY, BLAMES PRODUCERS

Firearms safety is usually taken very seriously – and even with fake guns people on set are supposed to follow stringent guidelines, agreed Syd Richardson, a production designer whose recent work includes the upcoming Bruce Willis flick "Wrong Place" and "Unto the Sun" with Asraf.

"The rule is always shoot at three degrees away from talent -- never shoot at talent, and that's just rule number one," he told Fox News Digital. "No one behind the gun. Never aim the gun at anyone."

Movie industry standards state that guns should never be pointed at anyone "unless absolutely necessary to do so on camera." They are never to be left unattended or used for "horseplay."

For rehearsals, actors don’t even need to be holding weapons at all, Richardson said. 

"A lot of times I do have dummy orange or bright pink guns, rehearsal guns, no mistake on that," he said, adding that he might even hand them a banana. 

Hutchins’ slaying occurred amid conflicting reports over safety conditions on set, alleged cost-cutting measures, and treatment of crew members. Faced with nondisclosure agreements and production company lawyers looking to clamp down on leaks, few people connected to the film have spoken out on the record. 

Lane Luper, the movie’s former first camera assistant who resigned in protest a day before the shooting, told "Good Morning America" Wednesday that he had concerns over the treatment of crew members by the production company as well as for on-set safety.

Despite the departure of his camera team, at least one "Rust" crew member disputed widely circulated claims of "unsafe, chaotic conditions" on a set where the cinematographer was killed and the director wounded by gunfire.

Terese Davis slammed the camera crew and complaints against production company Thomasville Pictures in a lengthy Facebook post. On Tuesday night, Baldwin reposted her missive.

But police said last week that they’d recovered real bullets from the set and that a lead slug had been pulled out of director Joel Souza’s shoulder.

Detectives are focusing on their investigation on two people who handled the gun shortly before Baldwin began rehearsing with it.

Dave Halls, the first assistant director on the film, allegedly handed Baldwin the weapon and told him it was "cold," or safe, according to the warrants. His attorney, Lisa Torraco, disputed the timeline laid out in warrants connected to the case in an interview with Fox News’s Martha MacCallum on Monday.

"In the affidavits it states that my client grabbed the gun off of a prop cart and handed it to Baldwin, that absolutely did not happen," she said, asserting that the movie’s armorer or assistant armorer brought the weapon in from the cart. 

She later avoided answering a question about whether Halls had handed the gun to Baldwin as outlined in the warrants. 

Gutierrez Reed, the armorer, said through her attorneys last week that producers were to blame for unsafe conditions on set. According to IATSE Local 480, a chapter of the International Alliance of Theatrical Stage Employees, her job should have included "continually check[ing] weapons during breaks and rehearsals, making sure safety controls are still intact."

Her attorneys appeared on NBC’s "Today" Wednesday and said they were looking into whether someone sabotaged a box of dummy ammo by planting real bullets. 

"I believe that somebody who would do that would want to sabotage the set, want to prove a point, want to say that they’re disgruntled, they’re unhappy," Jason Bowles told the show, arguing that the weapons were left unattended between 11 a.m. and after 1 p.m. on the day of the shooting and creating "opportunity" for such an act.

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Robert Gorence, a second attorney for Gutierrez Reed, doubled down on that window and added that the prop ammunition was kept separate from the firearms.

"The guns are locked in a safe, the prop ammunition was in a truck, the prop truck that was completely unattended at all times," he said. 

When asked if Gutierrez Reed had inspected the weapons again after the two-hour break to determine what was inside, her attorneys conceded that she did not.

Sources close to the set told Fox News that Hutchins’ injuries were so severe that on-set medics changed her bandages three times before a medical helicopter arrived. She later died.

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The round that tore through her, believed to be a .45 Long Colt, passed through and also wounded Souza, according to authorities.

A Baldwin spokeswoman did not respond to questions about whether an on-set shooting that left one dead and one hospitalized constituted "unsafe, chaotic conditions."