Actor Alec Baldwin and a weapons specialist will be charged with involuntary manslaughter in the fatal shooting of a cinematographer on a New Mexico movie set, prosecutors announced Thursday, citing a “criminal disregard for safety.”

Santa Fe District Attorney Mary Carmack-Altwies issued a statement announcing the charges against Mr. Baldwin and Hannah Gutierrez-Reed, who supervised weapons on the set of the Western “Rust.”

Halyna Hutchins died shortly after being wounded during rehearsals at a ranch on the outskirts of Santa Fe on October 21, 2021. Mr. Baldwin was pointing a pistol at Ms. Hutchins when the gun went off, killing her and wounding the director, Joel Souza.

Assistant director David Halls, who handed Baldwin the gun, has signed an agreement to plead guilty to negligent use of a deadly weapon, the district attorney’s office said.

Involuntary manslaughter can involve a killing that happens while a defendant is doing something that is lawful but dangerous and is acting negligently or without caution.

The charge is a fourth-degree felony, punishable by up to 18 months in jail and a $5,000 fine under New Mexico law. The charges also include a provision that could result in a mandatory five years in prison because the offense was committed with a gun.

Ms. Carmack-Altwies said charges will be filed by the end of January, and that Mr. Baldwin and Ms. Gutierrez-Reed will be issued a summons to appear in court. She said prosecutors will forgo a grand jury and rely on a judge to determine if there is probable cause to move toward trial.

Andrea Reeb, a special prosecutor on the case, cited a “pattern of criminal disregard for safety” on the film set.

“If any one of these three people — Alec Baldwin, Hannah Gutierrez-Reed or David Halls — had done their job, Halyna Hutchins would be alive today. It’s that simple,” said Ms. Reeb, also a newly sworn Republican state legislator.

Mr. Baldwin’s attorney said the charges represented “a terrible miscarriage of justice.”

The actor “had no reason to believe there was a live bullet in the gun — or anywhere on the movie set. He relied on the professionals with whom he worked, who assured him the gun did not have live rounds. We will fight these charges, and we will win,” Luke Nikas said in a statement.

An attorney for Ms. Gutierrez-Reed said the charges were “the result of a very flawed investigation and an inaccurate understanding of the full facts.”

“We intend to bring the full truth to light and believe Hannah will be exonerated of wrongdoing by a jury,” Jason Bowles said.

Santa Fe County Sheriff Adan Mendoza, who led the initial investigation into Ms. Hutchins’ 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 yearlong investigation in October. That report did not specify how live ammunition wound up on the film set.

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

He sought to clear his name by suing people involved in handling and supplying the loaded gun. Mr. Baldwin, also a co-producer on “Rust,” said he was told the gun was safe.

In his lawsuit, Mr. Baldwin said that while working on camera angles with Ms. Hutchins, he pointed the gun in her direction and pulled back and released the hammer of the weapon, 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.

New Mexico’s Occupational Health and Safety Bureau 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 the set prior to 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 gun safety.

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

Investigators initially found 500 rounds of ammunition at the movie set on the outskirts of Santa Fe — a mix of blanks, dummy rounds and what appeared to be live rounds. Industry experts have said live rounds should never be on set.

The family of Ms. Hutchins — widower Matthew Hutchins and son Andros — settled a lawsuit against producers under an agreement that aims to restart filming with Matthew Hutchin’s involvement as executive producer.

“Rust” was beset by disputes from the start in early October 2021. Seven crew members walked off the set just hours before the shooting amid discord over working conditions.

Ms. Hutchins’ death influenced negotiations over safety provisions in film crew union contracts with Hollywood producers. The shooting also spurred other filmmakers to minimize risks by using computer-generated imagery of gunfire rather than real weapons with blank ammunition.