(NewsNation Now) —  There are some disturbing new details about last week’s deadly shooting on the set of Alec Baldwin’s movie “Rust.” Investigators now say that the film’s cinematographer was killed by a live round that was recovered from the film’s director, who was wounded. Santa Fe authorities also seized three firearms and 500 rounds of ammunition — a mix of blanks, dummy rounds and suspected live rounds that were on the set. 

Bryan Carpenter, who works as an armorer and weapons expert for Dark Thirty Film Services, says he was shocked to hear that live rounds and dummy rounds were mixed on set. 

“The idea that they had found possibly multiple rounds and possibly multiple guns with rounds … it’s pretty, pretty hard to believe.” Carpenter, who joined “On Balance” on Thursday, said there is no reason why live rounds should ever be on a set. 

“Under no circumstances should it have been there. The only types of rounds that have any place on a movie set are blank rounds, and/or dummy rounds, which simulate the look of a real round, but are not.”

The evidence found on the set is now being investigated by the FBI. Halyna Hutchins was shot and killed last week on the New Mexico movie set after an assistant director allegedly unwittingly handed movie star Alec Baldwin a loaded weapon and told him it was safe to use for rehearsals.

An affidavit also says that the film’s assistant director, David Halls, did not fully check the whole revolver for live rounds before handing it to Baldwin.

Carpenter said there are several procedures and protocols when you handle prop guns on the set. One of them is to never point a gun directly at anyone. 

“Whether you’re in a tier-one operation group, or whether you’re training someone on a firing range, you follow these rules.” 

He also acknowledged that just because a gun looks like it’s pointed at someone on-camera, it never is. He said those types of shots are done in an off-angle. 

“It’s always done on any professional set that way; if it needs to be directed at camera or cameras locked off, it’s remote-operated.” 

Carpenter also noted the difference between a prop gun and a real gun.

“A prop gun is either plastic or rubber, hard rubber, soft rubber depending on what you’re using it for. They’re used for science, stunt scenes, fight scenes where the weapons are going to be banged around, hit with each other, any of those things,” he said. He said they can also be used for rehearsals. He added prop guns are only used “when there’s just absolutely no reason to bring out the other guy.” 

He said real guns used on set are supposed to have just blanks. He said, “They are simply real, and we call them ‘realies’ as a slang term on set.” 

Carpenter said generally, all actors meet with the armorer on set for safety training. He said this is why it’s hard to believe a shooting like this could happen.

“It begs to ask the question. Had he ever had safety training? Had anyone ever trained him to … the force safety rules? … You place a weapon in your hand, you take on a duty of safety.” 

Local prosecutors say it’s too early to tell if there will be criminal charges in the case.