My 12 year old cousin had his first (and hopefully last) ND this past week. He was pumping up his BB gun before he went outside to shoot and "it went off." His dad asked him if he had pulled the trigger. He said no. Upon hearing that his dad was taking said airgun and destroying it, as only a defective gun just goes off, he admitted to pulling the trigger.
I found out a few days later. I was PISSED and seriously let down. I had spent the most time with him teaching firearms safety. I asked him what happened, he said he accidently pulled the trigger, but it wasn't loaded so its not a big deal. DOH! ALL FIREARMS ARE ALWAYS LOADED!!!!
We had a little heart to heart about being safe. He now has to write an essay on firearms safety, the 4 rules, why they are important, and how he screwed up. I really hope that he learns a lesson from this. I had really high hopes for him. Up until now, he was safer than most adults I know, and in a few years could probably out shoot them as well.