Fortunately, the yelling was short, and was NOT related to the discharge. It was rather cool, actually.

He sights...he pauses....he starts to put the gun down with his finger still on the trigger...as he goes to lay the gun on the table...

BANG!

ME: "OK, you're done for the day, let's pack up." (I take the gun, clear it, check chamber, check it again)

HIM: "But DAD it was a mistake!"

ME: "I know, but you were not in control of your weapon, and you just had an accidental discharge - that's not acceptable"

HIM: "BUT THE TRIGGER DIDN'T WORK. IT WAS A MISTAKE!!! PLEASE CAN I TRY AGAIN!!"

ME: "Obviously, the trigger worked fine, as you shot the gun as you put it down. You know to keep off the trigger unless you're about to fire. We're done now."

THEN the hysterics started, and only then did I yell something to the effect of "YOU KNOW THE RULES HERE, AND YOU BROKE THEM. YOU ARE NOT SHOOTING AGAIN TONIGHT!"

So, while the discharge WAS downrange, on a "Hot" range, and the round definitely hit the berm (I saw it hit), it was a clearly my job to halt things at that point. He was truly sorry, he really did think it was a gun malfunction, I think he expected the trigger pull to be as light as his BB gun. We did "dry fire" with snap caps before going to live rounds, but still he's learning.