are and where armorer/prop-master responsibility ends. Sounds like a "rules are for other people" mentality was running the show, and a rookie armorer unable to stand up to them.
PLUS disgruntled workers walking off set just before the shooting. No idea when guns were laid out or who messed with them and when after they had been laid out.
More details will surely come out in the course of the investigation. Meanwhile, anything is possible.