...the prop gun had "misfired" several times already. Misfires are a problem in a self defense situation...but if you're shooting blank rounds in a movie production, a misfire is nothing more than an annoyance and certainly isn't a safety issue. This makes me wonder if they were having issues getting the gun to properly set off the primers on the blank rounds, so someone put a few live rounds in the gun for testing and simply never cleared the cylinder. Perhaps the gun did have blank rounds in it, but also contained a live round that was "next up" in the cylinder. That's obviously wild speculation, but it does make me wonder.

What a tragic situation, and one that's really hard to comprehend. There must have been multiple missteps along the way for this to have occurred.