I'm not employed at a range, but I volunteer as a RSO once a week.
I don't believe in Accidental Discharge. It's nearly always a Negligent Discharge. I guess it's the way you look at it. This was negligent. Loading a live round at a gun shop anyplace but on the range with the pointy end going down-range qualifies it. Unpleasant results from that point inherit the same description.
I do. Generally, though, accidental discharges don't hurt anyone because they go into a range backstop or other safe direction. Following the safety rules will usually ensure that any unexpected discharge is relatively harmless, and so usually if an unexpected discharge causes an injury it will be because of negigence on the part of the shooter.
Even there, however, there are exceptions. A firearm which discharges unexpectedly due to mechanical problems may injure the shooter's hand if it's near a slide or operating lever even if the shooter is obeying all safety rules. And I don't remember any safety rules about being ready for a firearm to start slam-firing full-auto (I recall reading of someone who was killed when his SKS did precisely that when he dropped the bolt).
Finally, there are some cases where obeying all the safety rules just plain isn't possible. For example, if one is cleaning out a deceased person's second-floor apartment and finds bolt-action rifle with the action closed and safety on "safe", what is a safe course of action? There is no safe direction to point the thing, and opening the action would require flipping the safety to "fire". While the latter operation shouldn't fire the weapon, some bolt-action rifles can fire when the safety is flipped. So what would be a prudent action in such circumstances?