Can't tell, did he have his finger on the trigger??
Israeli.
Slam fires can transpire when loading, especially in ARs, 870s, 1911s, or any firearm with an inertia firing pin.
My slam fire was with an 870s. The Four Rules light is always on.
Add SKS's to that list. They can empty a mag during a slam fire if the firing pin gets bent as a result of the first.
I replaced mine with a spring loaded pin that's meant to prevent that from happening.
$30 is cheap peace of mind.