'Rust' Assistant Director Admits Gun Safety Lapses Before Fatal Shooting

The head armorer on the set of "Rust" told authorities she took all the necessary steps to secure the gun that killed the cinematographer ... but the assistant director confessed the gun was not thoroughly checked before Alec Baldwin fired the fatal round.

According to a new search warrant, obtained by TMZ, Hannah Gutierrez-Reed told authorities the day of the shooting she had checked the ammo -- which she called the "dummies," meaning they were not live rounds. She added there were never live rounds on the set.

She went on to say the gun was locked up in a safe in a prop truck during the lunch break and taken out shortly before the fatal scene. The implication -- she's saying the gun appeared safe to her, because it wasn't messed with it during lunch. She did, however, say there were a few people who had access to the safe.

Assistant director David Halls -- the person who handed the weapon to Baldwin and called it a "cold gun" -- confessed when she showed him the firearm before rehearsal he could only remember seeing 3 rounds. He admitted he should have checked all of the rounds, and doesn't remember if Hannah spun the drum before she handed him the gun, and he, in turn, handed it to Baldwin.

After cinematographer Halyna Hutchins and director Joel Souza were shot, Halls says he inspected the chamber and he remembers seeing at least 4 dummy casings with the signature hole on the side, and one without the hole. He said the one without the hole didn't have a cap ... the implication is it was the remains of a live round of ammunition.

This all points to a lapse of safety precautions on the set, and that's something the District Attorney is now looking at in determining if criminal charges should be filed. The D.A. said charges are on the table for everyone involved. Authorities want to speak with Baldwin again and they want to review the employment history of both Halls and Gutierrez-Reed before making a filing decision.