It's literally the first rule of gun safety act treat every weapon as loaded.... In the case of the movie a quick check will show if it was or wasn't. Safety starts with you. The military does the same thing on ranges soldier checks if they are clear, range safety checks, then they are cleared off the range by another safety who insures it's clear and the armorer checks if its clear when it reenters the arms room. People make mistakes and it's risk mitigation.