SANTA FE, N.M.—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 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. Mendoza also told reporters there was a complacent attitude toward safety on the set before last Thursday’s shooting that killed cinematographer Halyna Hutchins during a rehearsal. 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 …