You can't be serious. How do you bring an AK47 in front of you if it's in your left hand and your right side is turning toward the front???
That pellet gun was never in a position to be a threat.
In order for it to have been a threat he would have to be facing the police with both hands on the gun but he was shot in the right side with the gun in his left.
By moving your left arm holding the gun forward and up while grasping the rising barrel with your right hand and moving it from left to center.
-btw If the police are positioned behind the teenager and to his left, turning to his right places his body between the police and the gun and conceals the weapon from their view regardless how he holds it.
You also might consider how 'normal' it is for someone to turn to their right in reaction to sound/stimulis from their left.
And again, absent the orange colored safety tip at the end of the gun barrel, in this scenario it is extremely unlikely the replica gun the teen was holding would be discernible from the real thing.