A true accidental discharge is very rare. Most “accidental discharges” are actually negligent discharges – something that was caused by ignoring the rules of firearm safety and making a mistake. A true accidental discharge only happens when all of the rules of firearm safety are followed and the gun still goes off – this is one of those times.
The shooter was being filmed by a tripod, not by a person down range, and he kept his finger off the trigger and the muzzle pointed down range at all times, but the firearm still went off.
This happened due to an incorrectly installed aftermarket hammer and sear that were labeled “gunsmith installation only” and he disabled the firing pin block on his firearm for a shorter reset. In other words, he modified his gun in a way it shouldn’t have to achieve a shorter trigger pull for competition. This incorrect firearm modification caused the gun to go off when chambering a round, even though he had already test fired it and put roughtly 1,000 rounds down range before the failure.
Listen to the range instructor’s words after the accidental discharge. This shooter did everything right while he was on the range, the only thing he did wrong was improperly modify his firearm. Always keep your finger off the trigger and always keep the firearm pointed in a safe direction, especially when loading and unloading the firearm.
This is why there are no exceptions to the rules of firearm safety. Accidental discharges can and will happen.