You're asking someone to make a lot of calculations in their head in a short amount of time. An airsoft AK weighs 5.7 lbs. A real AK, loaded, weighs a little over 9 pounds. That's a little more than a gallon of milk.
I'll wager you this isn't an Airsoft, and this kid totes it all day long.
He had all day not a short period of time. He's the one who chose to shoot within 10 seconds of seeing the kid -- and then emptied his weapon -- not a double tap -- but a full clip without giving the kid a chance to even fall to the ground without being shot a half dozen more times.
An airsoft AK weighs 5.7 lbs. A real AK, loaded, weighs a little over 9 pounds.
Is that loaded or unloaded?? How much would it weigh with a full clip -- another 5 lbs???
Even empty it's a pretty big difference especially when carrying it in the offhand clasped over the firing mechanism.
And that was just one of many clues that this vaunted firearms expert ignored.
And you will notice that the kid in picture is carrying his gun with two hands and a shoulder strap.