As authorities continue to investigate the fatal shooting by Alec Baldwin during a rehearsal film scene in New Mexico, questions are being raised about how the tragedy was able to occur on set.

Cinematographer Halyna Hutchins, 42, was killed when Baldwin discharged a prop firearm on the set of the western movie Rust on Thursday. The film’s director Joel Souza, who was standing behind her, was shot in the shoulder.

It is unclear why the gun contained a projectile. Baldwin, best known for films and TV shows including The Departed and 30 Rock, and for portraying Donald Trump on Saturday Night Live, has described Hutchins’ death as “a tragic accident”.

No one has been charged in relation to the incident, which happened at the Bonanza Creek Ranch outside Santa Fe. Santa Fe-area District Attorney Mary Carmack-Altwies has said prosecutors are reviewing evidence, while New Mexico workplace safety investigators are examining if film industry standards for gun safety were followed during production.

Several media and social media reports have raised concerns about safety protocols on what was a low-budget movie set.

Here is what we know about crew members on set and what witnesses have told authorities.

Armourer

The person in charge of weapons on set is known as an armourer. The armourer for Rust, Hannah Gutierrez-Reed, had set up the gun and two others, according to an affidavit from the Santa Fe County Sheriff’s Office.

The weapons were set on a cart outside the building where a scene was being rehearsed, court records say.

After the shooting, she removed a shell casing from the gun and turned the weapon over to police when they arrived, according to the court records.

Before taking up the role of armourer on a previous film, Ms Gutierrez-Reed reportedly said she wasn’t sure if she was ready for the position.

Speaking in an interview after completing a role as head armourer for the Nicolas Cage film The Old Way, Ms Gutierrez-Reed said: “‘I almost didn’t take the job because I wasn’t sure if I was ready, but doing it, it went really smoothly.”

She is also said to have admitted she found loading blanks into a gun “the scariest” thing and had sought help from her father, the renowned gunsmith Thell Reed, to overcome her fear.

Assistant director

It was the film’s assistant director Dave Halls who grabbed the gun from the cart and took it inside to Baldwin, unaware that it was loaded with live rounds, a detective wrote in a search warrant application for the film set.

He shouted “cold gun” – an industry term meaning a weapon is not loaded with ammunition, indicating that it was safe to use – before handing the firearm over, the search warrant states.

His film credits, according to IMDB, include The Matrix Reloaded, Bad Santa and The Crow: Salvation, a sequel to The Crow – which saw star Brandon Lee killed on set in a similar firearms incident in the 1990s.

Director

Rust director Joel Souza was standing behind Ms Hutchins and was shot in the shoulder during the incident. He was taken to hospital but later discharged.

At the time of the incident, Souza said he was focused on how the scene would appear on camera and that he recalled hearing the phrase “cold gun” being used, according to the affidavit.

He said the scene they were shooting did not call for the use of live rounds.

Cameraman

Camera operator Reid Russell gave a statement to detectives, telling them that Baldwin had been careful with weapons on set.

Mr Russell said the actor was rehearsing a scene in which he was set to draw his gun while sitting in a church pew and point it at the camera when the fatal shooting occurred.

He said he was unsure whether the weapon was checked before it was handed to Baldwin but that the camera was not rolling when the gun went off, according to the search warrant affidavit.

When asked about how Baldwin treated firearms on the set, Russell said the actor was very careful, giving details of an instance when Baldwin made sure a child actor was not near him when a gun was being discharged.

Speaking to detectives about the time on set leading up to the shooting, Russell said several members of the camera crew had walked off the production in a dispute over payment and lodging, and he was left with a lot of work to do.

Electrician/lighting professional

The film’s chief electrician Serge Svetnoy blamed producers for Ms Hutchins’ death in an emotional Facebook message posted on Sunday.

Mr Svetnoy said he had worked with Hutchins on multiple films and faulted “negligence and unprofessionalism” among those handling weapons on the set.

He also said that producers hired an inexperienced armourer.

Script supervisor

The film’s script supervisor, Mamie Mitchell, said she was standing next to Hutchins when she was shot.

Following the shooting, she quickly called emergency services, and details of the call were later released.

“I ran out and called 911 and said ‘Bring everybody, send everybody’,” Mitchell told The Associated Press. “This woman is gone at the beginning of her career. She was an extraordinary, rare, very rare woman.”

In the 911 call, Ms Mitchell is calm but clearly in a state of distress; background noises suggest people raced to get help for the two people who had been injured while the call was being made.

Asked by the operator if the gun was loaded with a real bullet, she replied: “I don’t, I cannot tell you that… we have two injuries from a movie gunshot.”

Unnamed crew members

A report in The Los Angeles Times, citing two crew members who were not named, said that five days before the shooting, Baldwin’s stunt double accidentally fired two live rounds after being told the gun did not have any ammunition.

A crew member who was alarmed by the misfires told a unit production manager in a text message, “We’ve now had 3 accidental discharges. This is super unsafe”, according to a copy of the message reviewed by the newspaper.

The New York Times, citing three former crew members, also reported that there were at least two earlier accidental gun discharges.

Rust Movie Productions said in a statement on Friday that it had not been aware of any safety concerns but was investigating claims of previous incidents.

“Though we were not made aware of any official complaints concerning weapon or prop safety on set, we will be conducting an internal review of our procedures while production is shut down,” it said.