Why do you mock? A gun doesn't just "go off". It's not some ticking timebomb that if you look at it wrong or toss it it will fire. Maybe it's just me because I was raised to understand firearms and handle them at an early age. The reports I read was he was "showing off" and wanted to "put the safety on". At age 15 I knew exactly how to handle firearms and the respect they need, just like a chainsaw.
That screams not knowing how to handle a firearm. Who's fault is that? The father/parents. If he felt he needed a weapon, he should know how to use it/operate it. Fault the father for not teaching how to handle firearms, fault the kid for not knowing, fault all you want.
Lemme guess, you think tossing a firearm to the ground makes it fire? Answer that, in this thread. I'll give you a clue, pulling the trigger makes it go bang.