IMHO i dont believe there is such a thing as accidental discharge. Guns dont just fire themselves unless we as operators have done something to make them go off. My unit pulled the word accidental out of all of our instructions, and only uses the word negligent now.
While I get where your unit is going with this…it doesn’t take into account the occasional weapons malfunction. Sometimes these things happen. In theory, guns don’t just go off, but they are mechanical devices. mechanical devices break, they wear out with use, have manufacture defects etc. You should only be held negligent for what you can control. you can’t control a mechanical failure that causes a rifle to discharge unexpectedly. But you can control where the gun is pointing at all times.
Which brings us back to the 4 rules. If you follow them, then any unexpected discharge should (in theory) only result in a red face and not tragedy.