It would be nice to know exactly what happened--so others can avoid the same mistake.
For example, one of the more obscure ND's I ever heard of was a cop holstering his gun in the winter. Well, the winter coat had those strings on the inside that can cinch it around a fella's waist. This particular coat didn't have knots in the string, it had toggles. Unknown to the cop, as he was holstering the gun, one of the toggles got caught in the trigger guard. Pay attention to that point. It means his finger was not in the trigger guard. Imagine, you follow safety rules and keep your finger out of the trigger guard; but, the absence of your finger inside the trigger guard allows a daggone jacket toggle to get into the trigger guard.
Well, later he goes to take off the coat. Of course, as he takes off the coat, the toggle on the end of the cinch string pulls up on the trigger with the usual result. Ouch!! And, massive surprise. "Why the hell did my gun just shoot me in the leg!?!?!?!" Can you imagine the total perplexity in that first second after the shot?
So, guess who has a winter coat with toggles? Yep. And, guess who now is very careful about making sure there are no strings, toggles, dead cats, or anything else that got caught while holstering. A light sweep of the finger tips after snapping the retention.
So, it would be nice to know from the NRA exactly what happened, so the rest of us can avoid it.