Bryan Carpenter has worked as an armorer  — the person responsible for overseeing weapons — on series such as “Queen of the South” and “Cloak & Dagger.” He has a lot of thoughts about what appears to have gone wrong on the set of the Alec Baldwin movie “Rust.” The biggest issue of all? The apparent presence of live ammunition. “That never should occur,” Carpenter says. “That would be the worst case scenario — to introduce a live round onto a movie set that’s using firearms.”Carpenter details the circumstances that contributed to the tragic death of cinematographer Halyna Hutchins, and he shares his hope that this nightmare will lead to more standardized gun safety training across the film industry.