Totally, a disgruntled union member could have slipped a live round in the prop knowing someone (a scab) would get shot, not caring who it was. There would have been some chaos going on while the union members and the scabs were all present at the same time (6:30AM) when they came to get their equipment. It would be easy to do it. Union members don't mess around when it comes to strikes and replacement workers. Although most people wouldn't do it, but a hard core union person might.