Alec Baldwin's gun from 'Rust' shooting found to be mechanically improper, sources tell ABC News

ABC News has learned more information as to why the involuntary manslaughter charge against Alec Baldwin following the fatal shooting on the set of "Rust" have been dropped.

Sources tell ABC News Baldwin's charges were dropped, in part, because investigators found the gun that killed cinematographer Halyna Hutchins to be mechanically improper. Therefore, it became evident to prosecutors that the gun could fire without pressure on the trigger.

Investigators effectively conducted an autopsy of the gun and found that there were worn joints. The trigger control was not functioning properly.

Baldwin had said previously that he did not pull the trigger when the gun he was holding shot Hutchins.

Prosecutors in Santa Fe, New Mexico formally dropped Baldwin's charge on Friday.

Involuntary manslaughter charges are still in place against Hannah Gutierrez-Reed, the weapons supervisor on the film.

Her pre-trial hearing is set for August.