...He wasn't paying particular attention and had just returned from being outside with the rifle. The safety was off, and there was a round in the chamber (you see this coming don't you!). Years ago - '89 or so, IIRC, a secretary at my office asked me how she should go about selling some guns that had belonged to her father. Naturally, I felt obliged to help. :-)
I asked whether she knew what the makes and models were, but all she knew was that there were five long guns cased in her hall closet, where they'd been since her dad passed away years before. Her husband was clueless about guns, so I offered to have a look and bring the guns to a local gunshop to get an appraisal.
My instructions were simple: Don't touch the guns, just leave them in the cases and put them in your car trunk. Easy, right? Well, she showed up the next day and opened her trunk. As I moved the cases to my car, I noticed one of the cases had a bullet hole in the end. Poking my finger in the frayed puncture, I looked at her with an eyebrow raised.
She got a sheepish look on her face, then 'fessed-up. Fearing the guns would be dusty and unsightly, she decided to partially open the cases and wipe them off. That case held a Winchester 94, and somehow she managed to work the lever and then, when dusting, she hit the trigger.
Luckily, the bullet went through an outside wall in a direction that posed no danger to her neighbors. After her ears stopped ringing, she tried to conceal her little mistake by hanging a picture over the bullet hole.
She told me that her husband noticed the new picture and discovered the hole right away. She couldn't figure why he'd been suspicious of what was behind the picture, until I mentioned that he'd probably seen the bullet hole on the *outside* of that wall. "Ohhhh...", she replied.
*sigh*
A/Ds and close quarters discharges are NOT pleasant. I've taught all of my young adults how to effectively handle a great many small arms and we started when they were under 10. One "incident" in particular comes to mind. :-) My 13 yr old is a larger person. He's not fat, just a big guy. So he was able to learn to use the AR-15, A2 model when he was about 8. I was showing him how to "shoot-n-scoot" on a CQB range that we had down the hill from our house...we were also doing some least dominant hand/eye shooting. We had concluded the shoot and I told everybody there (there were about 5 of us) to make all the weapons SAFE. This meant that mags were removed, bolts locked to the rear and then let the "safety guy" (me in this instance) check them and send them to another small area on the range until everybody was checked. I watched my son unload his rifle, but before he dropped the magazine, he racked the charging handle and simply stripped another round from the magazine. So when I came to him, I TOLD him to unload the rifle. He told me that he ALREADY unloaded the rifle. I said, "NO. You did NOT. Now unload it!" Again he replied that the rifle was UNLOADED. He was carrying it slung topside and the muzzle was pointed at the ground several inches to his left of his left foot. I stepped forward, turned the selector switch to "fire", pointed the muzzle a little farther away from his foot and pulled the trigger! *KA-BOOM*... to which I replied. "NOW the rifle is unloaded! He looked at me like he had just seen a ghost. :-) I told him to give ME the rifle and go to the house to his MOTHER....shame!...shame!....shame! :-)
When I got to the house later, I covered what he had done incorrectly and he understood. I told him that the next time I had to interrogate him to get him to clear a weapon that I would beat him in front of the other guys....which would be secondary to him being a hazard with a firearm!
He will never, EVER forget the incident and is now one of the safest shooters I know! He's my primary shooting partner right now. :-) If he hands me a weapon, and tells me it's unloaded, I believe him! I still check though...as we all should! :-)