I've never had an accidental discharge of a firearm, but back when I was in the junior NRA rimfire program I avoided such an incident by pure happenstance. I liked to dry-fire praqctice in my upstairs bedroom using empty brass, and one evening I closed the bolt and found the trigger had already let off. The bolt noise must have screened that of the pin. Tried again, same thing, so I took the old Mossberg and some brass down to my dad. He quickly diagnosed trigger creep (I'd enjoyed the hair trigger), and adjusted it to 2.5 lb, sealed with a dot of glue. Had I not dry-fired that week, the following Saturday at the range I probably would've sent 40 grains of lead over the backstop hill.
I was present at one accidental discharge at age 14, at that time the minimum age for a regular NJ hunting license. A friend was showing me his recent gift of a .30-.30 (for out of state use only, rifles illegal in NJ then and now) and I should've spoken up as he showed me how to load it. Next thing I recall was dust settling from ceiling and walls, and the thunder of parents charging toward the room. His mom gently told me I ought to go home, but as I walked away from the house the swats and cries were plainly audible. Fortunately, for both of us, he had been pointing the weapon in a safe direction, the bullet exiting thru the crown molding above his closet.