The actor Alec Baldwin is facing criminal charges of involuntary manslaughter over the fatal film-set shooting of a cinematographer during a rehearsal of the western film Rust, according to prosecutors.

The film’s armorer overseeing weapons, Hannah Gutierrez Reed, is also set to be charged with involuntary manslaughter over the shooting death of Halyna Hutchins in Santa Fe, New Mexico, in 2021.

Meanwhile, the production’s assistant director, David Halls, has agreed to plead guilty to a misdemeanor charge of negligent use of a deadly weapon and to spend six months serving probation.

The Santa Fe district attorney, Mary Carmack-Altwies, announced the charges and plea deal on Thursday in a statement and on social media, without public appearances by prosecutors. Carmack-Altwies said the charges against both Baldwin and Gutierrez Reed had not yet been filed on Thursday, but would be before the end of January.

“On my watch, no one is above the law, and everyone deserves justice,” Carmack-Altwies’s statement said. A statement attributed to the prosecutor Carmack-Altwies appointed to the case, Andrea Reeb, added: “If any of these three people – Alec Baldwin, Hannah Gutierrez Reed or David Halls – had done their job, Halyna Hutchins would be alive today.”

An attorney for Baldwin, Luke Nikas, said his client “had no reason to believe there was a live bullet in the gun” on the day Hutchins was killed, and condemned the charges against the actor as “a terrible miscarriage of justice”.

“We will fight these charges,” Nikas’s statement said. “And we will win.”

An attorney for Gutierrez Reed, Jason Bowles, said Thursday that he believed jurors would acquit his client of wrongdoing.

And an attorney for Hutchins’s husband, Matt Hutchins, issued his own statement thanking Carmack-Altwies and calling the charges her office plans to pursue “a comfort”.

“We … fervently hope the justice system works to protect the public and hold accountable those who break the law,” said the statement attributed to attorney Brian Panish.

Carmack-Altwies’s office also announced that Rust’s director, Joel Souza, would not face any charges in connection with the shooting death of the 42-year-old Hutchins. Souza had been shot and injured alongside Hutchins on the day she was mortally wounded.

Hutchins died shortly after being shot during setup for a scene at a ranch on the outskirts of Santa Fe on 21 October 2021. Baldwin was pointing a pistol at Hutchins when the gun went off, killing her and wounding Souza.

Santa Fe’s county sheriff, Adan Mendoza, who led the initial investigation into Hutchins’s death, described “a degree of neglect” on the film set. But he left decisions about potential criminal charges to prosecutors after delivering the results of a year-long investigation in October. That report did not specify how live ammunition wound up on the film set.

Taking control of the investigation, Carmack-Altwies was granted an emergency $300,000 request for the state to pay for a special prosecutor, special investigator and other experts and personnel.

On Thursday, she said her office was prepared to ask a jury to convict Baldwin and Gutierrez Reed of involuntary manslaughter or – “in the alternative” – of involuntary manslaughter in the commission of a lawful act.

Under New Mexico law, involuntary manslaughter – which in this case carries with it a misdemeanor charge of negligent use of a firearm – would require prosecutors to prove that Hutchins died as a result of some underlying negligence.

Involuntary manslaughter in the commission of a lawful act, meanwhile, would require prosecutors to prove that there was more than simple negligence involved in Hutchins’s death.

Both charges are felonies typically carrying maximum penalties of 18 months in prison and a $5,000 fine. But, in this case, Carmack-Altwies’s office has added a so-called firearm enhancement to the involuntary manslaughter in the commission of a lawful act charge, meaning anyone convicted of that count would be required to spend five years in prison.

Baldwin – known for his roles in 30 Rock and The Hunt for Red October and his impression of Donald Trump on Saturday Night Live – has described the killing of Hutchins as a “tragic accident”.

Baldwin last year settled a wrongful death lawsuit filed by Hutchins’s family for an undisclosed sum. He has sought to clear his name by suing people involved in handling and supplying the loaded gun that was handed to him on set. Baldwin, also a co-producer on Rust, said he was told the gun was safe.

In his lawsuit, Baldwin said that while working on camera angles with Hutchins during rehearsal for a scene, he pointed the gun in her direction and pulled back and released the hammer of the gun, which discharged.

New Mexico’s office of the medical investigator determined the shooting was an accident following the completion of an autopsy and a review of law enforcement reports.

The occupational health and safety bureau in New Mexico has levied the maximum fine against Rust Movie Productions, based on a scathing narrative of safety failures, including testimony that production managers took limited or no action to address two misfires of blank ammunition on set before the fatal shooting.

Rust Movie Productions continues to challenge the basis of a $137,000 fine by regulators who say production managers on the set failed to follow standard industry protocols for firearms safety.

Gutierrez Reed in particular has been the subject of much of the scrutiny in the case, along with an independent ammunition supplier. An attorney for Gutierrez Reed has said the armorer did not put a live round in the gun that killed Hutchins, and believes she was the victim of sabotage. Authorities said they had found no evidence of that.

Once the charges announced on Thursday are filed, Baldwin and Gutierrez Reed would be arraigned and then be required to appear at a preliminary hearing where a judge will determine whether there is probable cause for them to proceed toward a trial. A date for that proceeding hasn’t been set, but it typically happens within 60 days of charges being filed, according to Carmack-Altwies’s office.

An attorney representing Halls, Lisa Tarraco, said her client’s plea deal let him move on with his life while returning the case’s focus to “the victims and changing the industry so this type of accident will never happen again”.

The Associated Press contributed reporting