Alec Baldwin has expressed his deep “shock and sadness” after he accidentally shot and killed his director of photography with an apparent real bullet on the set of his latest movie.

The actor was acting in or rehearsing for the western Rust when he discharged what he thought was a prop firearm. The cinematographer Halyna Hutchins was fatally struck and the director Joel Souza was wounded, the Santa Fe sheriff’s office said.

Despite attempts to save her, Hutchins was pronounced dead after being flown by helicopter to the University of New Mexico hospital. Souza was being treated at Christus St Vincent regional medical centre, where he was brought by ambulance.

On Friday, Baldwin tweeted: “There are no words to convey my shock and sadness regarding the tragic accident that took the life of Halyna Hutchins, a wife, mother and deeply admired colleague of ours. I’m fully cooperating with the police investigation to address how this tragedy occurred.”

A report emerged on Friday afternoon that a group of camera crew workers had walked off the set in a protest about poor working conditions, according to the Los Angeles Times.

Meanwhile, the Hollywood actor said he was in touch with Hutchins’ husband, Matthew, with whom she had a young son. “[I’m] offering my support to him and his family. My heart is broken for her husband, their son, and all who knew and loved Halyna,” Baldwin said.

The sheriff’s office said no charges had been brought following what appeared to be a tragic accident. The 63-year-old actor went “voluntarily” to the Santa Fe county office and spoke with investigators, spokesperson Juan Rios said.

The incident happened at 1.50pm local time on Thursday. Baldwin was spotted in the parking lot outside the sheriff’s building, speaking on the phone and visibly upset, the Santa Fe New Mexican newspaper reported.

Court records show that Baldwin was given a loaded weapon by an assistant director who indicated it was safe to use. The assistant director did not know the prop contained live rounds, according to a search warrant.

Detectives are likely to examine why the prop gun went off with such catastrophic consequences. In an email to its members on Friday, the entertainment union IATSE claimed the gun had contained a “single live round”. The weapon was “accidentally fired” by the “principal actor”, it added.

One Hollywood website, quoting a witness, said a distraught Baldwin had asked why he had been given a firearm apparently loaded with real ammunition. “In all my years, I’ve never been handed a hot gun,” he exclaimed, according to the site Showbiz 411.

Production on the western has been indefinitely halted, its producers said on Friday. The film was being shot in Bonanza Creek Ranch, a purpose-built set featuring log cabins, an authentic wooden church and an arid brown landscape, in the foothills of northern New Mexico.

The location, popular with film-makers, was the period setting for Tom Hanks’s 2020 film, News of the World. Rust, set in 1880s Kansas, tells the story of a 13-year-old boy who is left to fend for himself and his younger brother after the death of their parents. Baldwin plays the boy’s grandfather.

The actor was also producing the movie, while Souza directed and wrote the script. Hutchins, who was born in Ukraine, was director of photography. Friends on Friday praised her warmth, energy and collegiality, and said she had reached the top of a traditionally male-dominated profession.

Friend and fellow film-maker Elle Schneider told BBC Radio 4’s World at One programme that Hutchins was a “talented, dedicated artist”.

Then on Friday, the LA Times reported that the group of about six camera crew workers – operators and assistants – who had walked off set were angry about working conditions on what the paper described as a low-budget movie where it said “labor trouble had been brewing for days”.

The crew complaints involved allegations of overly long hours and an unfair pay situation, three people who were familiar with the matter but not authorized to speak out officially told the publication.

There was a dispute about the provision of hotel rooms and other labor matters, including safety, and Hutchins had made efforts to advocate for better conditions for her colleagues, a crew member told the LA Times, which included in its report that there were complaints about safety specifically involving prop guns.

Those who left the set are understood to have belonged to the International Alliance of Theatrical Stage Employees (IATSE), members of which more widely were recently on the brink of a strike, citing deteriorating and insupportable working conditions for workers.

Meanwhile, in further tribute to Hutchins, her friend Schneider had added: “She was just as invested in her friends’ success as she was in her own. She was just incredibly passionate about her work, collaborators, and friends, and fellow women coming up alongside her. She was fun to be around. She had an energetic and magnetic personality.”

“I’m so sad about losing Halyna. And so infuriated that this could happen on a set,” said Adam Egypt Mortimer, a director who had worked with Hutchins last year on the film Archenemy. “She was a brilliant talent who was absolutely committed to art and to film.”

According to her website, Hutchins grew up on a Soviet military base in the Arctic Circle surrounded “by reindeer and nuclear submarines”. An “army brat”, she became interested in film because there was “nothing much else to do”, she said. She cited the 1957 Soviet war film The Cranes Are Flying as an influence.

In 2019 she was named a “rising star” by American Cinematographer.

Accidents like the one that befell Hutchins have happened before. In 1993, Brandon Lee, the 28-year-old son of the late martial arts star Bruce Lee, died after being hit by a .44-calibre slug while filming a death scene for the movie The Crow. The gun was supposed to have fired a blank, but an autopsy turned up a bullet lodged near his spine.

• The Associated Press contributed reporting