It was a Glock, so there was no "safety" other than keeping your finger off the trigger, which is basic gun safety.
What happened is that he declared the bun unloaded, but left in a loaded magazine, thus charging the chamber with a round when he released the slide.
Glocks (really any centerfire pistol) are safe to "dry fire," and he was probably used to releasing the firing pin after pulling this stunt numerous times.
What really says it all is his claim of professionalism before he appears to shoot himself in the leg.
Sad to say, but I have had an Accidental discharge of the same type with a Glock.
Thank God the wife wasn't home, although she knows about it.
I was getting used to the trigger pull and release of the gun. (this is basic in knowing your weapon - where [in the pull] the trigger releases the hammer or firing pin)
I was sitting in the living room, practicing dry firing, put a magazine in, racked one in, absentmindedly, and while holding the gun pointing up at the ceiling, (beside my head) I squeezed the trigger.
My ears rang for a day.
I immediately started patching the small hole in the roof, and in the drop ceiling.
After numerous sessions at the bathroom mirror, invoking the truth that I was a dumba$$,
I thanked God it didn't hurt or kill anyone, and since then,
I cannot be too careful. Paranoia is ok when it comes to gun safety, or any other safety that can hurt or maim.
This guy got his spanking, but that doesn't keep me from LMAO at his bravado turned to stupidity.
What a blast.
