Several years ago an adult was killed by his own rifle, an SKS. Stored with the hammer not cocked, the firing pin rusted tight to the bolt.
When he loaded the rifle and released the bolt, the rifle slam fired all ten rounds, the recoil made him lose control and the rifle recoil flipped the rifle back and killed the shooter.
Re post #4: I hate it when that happens. Bad maintenance of course, but seems highly unusual, nonetheless.