ALEC BALDWIN in a scene from Rust. — IMDB.COM

SANTA FE, New Mexico — A New Mexico jury on Wednesday found Rust armorer Hannah Gutierrez guilty of involuntary manslaughter, ending a trial over Hollywood’s first on-set fatal shooting in nearly 30 years.

Ten days of testimony had focused on whether the relatively inexperienced armorer endangered fellow crew and cast members in her handling and supervision of firearms on the low-budget production set in New Mexico.

Judge Mary Marlowe Sommer ordered that Ms. Gutierrez be taken into custody immediately. She faces up to 18 months in state prison.

As deputies led her from the courtroom, Ms. Gutierrez told her distraught mother, “I’ll be okay.”

Jurors, who reached their decision in just three hours, acquitted Ms. Gutierrez on a second charge of evidence tampering.

Just after lunch on Oct. 21, 2021, Gutierrez mistakenly loaded a live round into a reproduction Colt .45 revolver that actor Alec Baldwin was using inside a movie-set church outside Santa Fe.

Mr. Baldwin cocked the gun, pointed it toward the camera and it fired one live bullet that killed cinematographer Halyna Hutchins and wounded director Joel Souza. Mr. Baldwin denies having pulled the trigger. His own manslaughter trial is set for July 10.

“This case is about constant, never-ending safety failures that resulted in the death of a human being and nearly killed another,” said New Mexico state special prosecutor Kari Morrissey in her closing statements earlier Wednesday.

Ms. Gutierrez’s lawyer Jason Bowles said he would appeal the decision. “My sense was the evidence was insufficient and it was a lot of speculation,” Mr. Bowles said outside the courthouse following the decision.

During the trial Mr. Bowles argued that the movie’s production company tried to cut costs by employing Ms. Gutierrez as both a part-time armorer and a props assistant in the gun-heavy Western. During the trial, movie-set firearms safety expert Bryan Carpenter testified that more armorers were needed on the set.

New Mexico’s worker safety agency in 2022 fined the company, Rust Media Productions, the state’s maximum possible penalty for ignoring industry firearm safety guidelines.

As one of the least experienced, least powerful people on set, lawyer Bowles said his client was taking the blame for management. “You’ve got a convenient fall person, a convenient scapegoat,” said Mr. Bowles.

‘RUSSIAN ROULETTE’Throughout the trial witnesses ranging from director Souza to assistant director Dave Halls said it was beyond anyone’s imagination that live rounds could be mingled in with dummy rounds on the production.

State prosecutors and defense lawyers have fought over the source of live rounds, which are strictly forbidden on movie sets.

Juror Alberto Sanchez, a truck driver, said the jury of six women and six men believed Ms. Gutierrez brought the rounds on set. “That was her job to check those rounds, those firearms,” he told reporters after the verdict.

During the trial a Santa Fe detective cited “circumstantial evidence” that Ms. Gutierrez unknowingly brought the live rounds to Rust from a previous production in a white cardboard box.

Morrissey gave jurors photos taken up to 10 days before the shooting showing a live round in the box and one in Mr. Baldwin’s bandolier.

“That’s a mountain of circumstantial evidence,” Morrissey said. “This was a game of Russian roulette every time an actor had a gun loaded with dummies.”

Bowles repeatedly blamed props supplier Seth Kenney, who has not been charged, as the source of the live rounds. He said Kenney, a weapons consultant on movies like Man Down and a props supplier to The Walking Dead, was not searched until a month after the shooting, allowing him to potentially dispose of evidence from his Albuquerque office.

Without knowing live rounds were on set, Mr. Bowles said Ms. Gutierrez did not show “willful disregard” for the safety of others, a requirement to convict her of involuntary manslaughter or a lesser charge of negligent use of a firearm, which carries up to six months in jail.

Half a dozen Rust crew members called by prosecutors testified that safety meetings were skipped, that Ms. Gutierrez sometimes failed to check whether weapons were loaded, and that Mr. Baldwin broke basic firearms safety rules.

BALDWIN’S ROLEIn the courthouse jurors last week watched video of Alec Baldwin rushing from a shack and blazing away with his Colt .45 “Peacemaker” revolver until he runs out of rounds.

“One more, one more, one more, right away, let’s reload,” Mr. Baldwin tells Ms. Gutierrez, saying she should have had a second gun already loaded.

Prosecutors had charged that Ms. Gutierrez rushed the handling of weapons, while failing to tell Mr. Baldwin, who was acting, not to point a gun at people or pull the trigger after a take.

Prosecutors used videos taken on the set to portray a breakdown of movie-industry firearm safety during the filming of Rust.

While setting up a scene, a video showed, Mr. Baldwin pointed a revolver at Ms. Hutchins; the weapon fired and fatally struck the cinematographer with a live round that had been mistakenly loaded by Ms. Gutierrez.

Even as Ms. Gutierrez stood trial, witnesses — including people who worked with her on Rust and firearms experts — touched on Mr. Baldwin’s role in the shooting. Some of the testimony suggested he was negligent and held a disproportionate amount of power on a set where he was a producer, writer, and lead actor.

In one video, for instance, Mr. Baldwin shouts an expletive and fires a last round after a crew member yells “cut,” breaking with movie set conventions and standards.

State prosecutors — and even Mr. Baldwin’s defense lawyers — will undoubtedly lean on some of the evidence introduced in the case against Ms. Gutierrez when Mr. Baldwin faces a July 10 manslaughter trial over Ms. Hutchins death, legal experts said.

On several occasions, Ms. Gutierrez’s defense lawyers asked witnesses whether Mr. Baldwin and veteran first assistant director Dave Halls prevented the rookie armorer from performing her weapons safety duties.

“He’s basically instructing the armorer how to do their job,” testified Bryan Carpenter, an expert in firearms safety on film sets who worked on around 100 films and TV episodes, after watching the Baldwin video clip. “Control is how we enforce gun safety.”

Attorney Jason Bowles asked Mr. Carpenter whether any armorer could have told Mr. Baldwin what to do. “It would be a difficult situation,” Mr. Carpenter testified.

DIFFERING TESTIMONIESCrew members, including Ross Addagio, who operated a camera dolly on the set, expressed similar concerns about Baldwin’s powerful role on the low-budget film.

“I don’t recall anybody standing up to Mr. Baldwin on the set of Rust,” testified Addagio, who also described Gutierrez as less “professional and serious” than other armorers he worked with.

Baldwin has said he was only a creative producer on the movie, rather than managing on-set operations, and as an actor he was not responsible for gun safety. He said he was directed to point his revolver at the camera when it fired the round.

Under cross examination by defense attorneys, Rust set stills photographer Karen Kuehn said Mr. Baldwin was the most powerful producer on set. She described him as the “boss” and said she did not see anyone say “no” to him.

Mr. Baldwin’s lawyers did not immediately respond to a request for comment. But legal experts said they, too, may take some beneficial testimony from the current trial.

Mr. Halls, the first assistant director who has already been convicted in the case, defended Mr. Baldwin, saying he behaved like many other actors caught up in the adrenalin of filming. “There was never any Mr. Baldwin rushing anyone,” said Mr. Halls.

That sort of testimony will likely find its way into Mr. Baldwin’s case, said Stephen Aarons, a Santa Fe criminal defense lawyer. “Baldwin’s crew will use some of this stuff and repeat it at his trial,” said Aarons.

State prosecutor Kari Morrissey on Wednesday used a moment of her closing argument in Ms. Gutierrez’s case to the set the stage for the upcoming trial of Baldwin. “Alec Baldwin’s conduct and his lack of gun safety inside that church on that day is something he’s going to have to answer for another day,” Ms. Morrissey told jurors. — Reuters