SANTA FE, NEW MEXICO (REUTERS) - A .45 caliber Colt pistol used on the set of the film Rust was not thoroughly checked before being given to actor Alec Baldwin, who fired a live lead bullet in an accidental fatal shooting last week in New Mexico, according to officials and a new court filing.

New details about the incident emerged on Wednesday (Oct 27) during a news conference by Santa Fe County Sheriff Adan Mendoza and District Attorney Mary Carmack-Altwies and in an affidavit filed by the local sheriff's department.

Mr Mendoza also told reporters there had been a complacent attitude towards safety on the set before last Thursday's shooting, which killed cinematographer Halyna Hutchins during a rehearsal.

Ms Hannah Gutierrez, the crew member in charge of weapons on the set, told investigators that she had checked guns there but found no "hot rounds" - apparently meaning live ammunition - before the shooting, according to the affidavit filed by the Santa Fe County Sheriff's Department.

Mr Dave Halls, the film's assistant director, told investigators he "should have checked all" the rounds in the gun before handing it to Baldwin but had not done so, according to the affidavit.

Authorities have said previously that Baldwin was handed what he thought was a "cold," or safe, gun by Mr Halls, who took it from a cart used by Ms Gutierrez.

Mr Mendoza and Ms Carmack-Altwies said that while no charges have been filed, they are not ruling out that possibility.

"All options are on the table... No one has been ruled out at this point," Ms Carmack-Altwies said, referring to potential criminal charges.

Ms Gutierrez, whose job is formally known as the film crew's armorer, said ammunition was not secured on the set during a lunch break taken before the shooting, the affidavit showed. It quoted her as saying that firearms were secured inside a safe during the break and that no live ammunition is ever kept on a movie set.

Mr Mendoza said that authorities have collected 600 pieces of evidence including three firearms, 500 rounds of ammunition - some believed to be live bullets - and several pieces of clothing and accessories in the ongoing investigation.

Some evidence is being sent to a Federal Bureau of Investigation crime lab for analysis, he said.

Authorities have the firearm used in the shooting, he added, and they recovered the bullet from the shoulder of director Joel Souza, who was wounded but later released from the hospital. Mr Mendoza said it appears the same bullet struck Mr Souza and the late Ms Hutchins.

Mr Mendoza said the gun used by the actor was an Italian-made Pietta Long Colt revolver.

"We would consider it a live round - a bullet, live - because it did fire from the weapon and obviously caused the death of Ms Hutchins and injured Mr Souza," Mr Mendoza said.

Mr Mendoza said Baldwin, Mr Halls and Ms Gutierrez are all cooperating with the investigation.

Asked about the use of real weapons on a movie set, the sheriff said: "I think the industry has had a record recently of being safe. I think there was some complacency on this set. And I think there are some safety issues that need to be addressed by the industry and possibly by the state of New Mexico."

The shooting has sent shockwaves through Hollywood, prompting a debate about safety protocols in film and television - including whether certain types of guns used as props should be banned - and working conditions on low-budget productions.

Before the incident, camera operators had walked off the set to protest working conditions, according to the affidavit.

Baldwin, 63, serves as a co-producer of Rust, a Western film set in 1880s Kansas. Production on the Bonanza Creek Ranch, near Santa Fe, has been halted.

He was drawing a revolver across his body and pointing it at a camera while rehearsing when the weapon fired, according to court documents. There is no video footage of the incident, Mr Mendoza said.

The film's producers have hired the law firm Jenner & Block to investigate the shooting. In a letter sent to cast and crew on Tuesday night, the film's production team said the firm "will have full discretion about who to interview and any conclusions they draw".