Alec Baldwin was formally charged Tuesday with involuntary manslaughter over the accidental shooting of a cinematographer on the set of the low-budget western "Rust."

Baldwin was holding the Colt .45 during rehearsals for the film when it discharged, killing Halyna Hutchins in October 2021.

New Mexico First Judicial District Attorney Mary Carmack-Altwies had already announced earlier this month that there was sufficient evidence to file criminal charges against the veteran US actor.

"Today we have taken another important step in securing justice for Halyna Hutchins," Carmack-Altwies said Tuesday. "In New Mexico, no one is above the law and justice will be served."

In their statement of probable cause, investigators said Baldwin had been "distracted and talking on his cell phone to his family" during a firearms training session.

He only attended training for around 30 minutes, even though the session was scheduled to run for "at least an hour or more," they wrote, citing the film's armorer Hannah Gutierrez-Reed.

Gutierrez-Reed, who was responsible for weapons on set, was formally charged Tuesday with the same crime as Baldwin.

If convicted, they face up to 18 months in prison and a $5,000 fine, but a firearm enhancement to the charge could take that sentence to five years.

Former "30 Rock" star Baldwin has repeatedly said he was told by the crew that the gun was not loaded, and that he did not pull the trigger.

Baldwin's attorney Luke Nikas has vowed to beat the charge, which he called a "terrible miscarriage of justice."

Lawyers for Gutierrez-Reed said Tuesday that prosecutors had "completely misunderstood the facts" and had "reached the wrong conclusions."

"We will fight these charges and expect that a jury will find Hannah not guilty," said Jason Bowles and Todd Bullion.

Separately, "Rust" assistant director Dave Halls, who handed Baldwin the weapon and told him it was "cold" -- industry speak for safe -- pleaded no contest to negligent use of a deadly weapon.

His plea agreement will be made public after a judge's approval.

Baldwin, a co-producer of the movie, and Gutierrez-Reed have both been charged with two alternative counts of manslaughter, each involving different levels of negligence.

Both counts entail a maximum 18-month jail term, but one of them -- involuntary manslaughter in the commission of a lawful act -- includes an added mandatory penalty of five years' jail because a gun was involved in the death.

New Mexico prosecutors will summon the accused to appear in court within a month of Tuesday's filing.