Well this all depends on the airsoft gun and lets be straight here.
This is a BBgun ^
This is a Airsoft gun
If someone pointed a airsoft gun which a lot of the time has no indication of being fake and if it did it is likely painted black or removed after buying to give that realism effect I would shoot them not reach for my tazer because i'm "in fear for my life" That's why he was shot and not tazed end of story.
"You shoot for the upper body" That's where you shoot in order to quickly stop a threat and yes the kid was a threat.
Why did your fucking kid have a airsoft gun out in public aiming it at police?