I don't get how he did that. Is he resting the barrel on his left hand?

Then he walks off the line with a loaded gun. Don't ever under any circumstances walk off the line with a live gun, you could face litigation, let alone an angry range officer (They can physically take the gun from you). Range discipline keeps you and others safe, and it starts with proper shooting technique.

He looks the be left eye dominant shooting right handed. Don't push the gun to your left Eye,just tilt it over towards the left eye while maintaining muzzle discipline.

It looks like the little handle on the pistol broke, or maybe it was detached. The pistol is small, use hands to hold it not a piece of plastic.

I dislike the Isosceles stance, i would recommend a modified weaver stance.

Isosceles tends to be less accurate with recoil dissipating in the arm that is not extended to its most structural point. With the weaver you have 100% dissipation in both arms with a strong base, that also allows the enemy to have an enticing target of your armor plates, and not your unarmored sides.

The Isosceles stance was created for a man with an injury to his arm that made it tough for him to take a proper weaver.

This looks like some cheap DIY modifications, if the knowledge behind modification is lacking ask a gunsmith.

I don't think a safety officer would blame a guy for still holding a loaded gun if he has half his hand shot off.

"it's just a flesh wound!"

Hm. I'm going to go with not shot. Maybe his off-hand got caught up in the action and it nipped him. Given the way he was resting the pistol, it looks like the mainspring housing could have got him and taken a chunk out.

^You miss the slow-mo of it pointing right at his hand and shooting, and seeing the hole in his hand?