Shoot to KILL!

How many policemen does it take to kill a high school student?

Obviously, as many as wants to join in.

But of more concern to me is where did this notion that any
and all armed suspects are automatically targets for
police pistol-practice and it became Standard Operating
Procedure?
Where did we get the idea that a sharpshooter MUST aim
for vital organs? It sort of makes a lie of the title of
"sharpshooter," doesn't it?

Shouldn't a police officer be instilled with the idea that in
order to disarm a suspect with a weapon, or dummy weapon,
a well placed bullet to the knee or elbow would be sufficient
to cause an armed person to change their focus, their stance
or possibly drop the weapon altogether?

Is "Drop it NOW or DIE!" the only options?