Not to sound like an asshole here, but if what the cops said is true - that kid was extremely stupid. Carrying a realistic looking airsoft gun in public view, not raising his hands, reaching for the gun, removing the orange tip... etc.
It's unfortunate that the cop wasn't informed that it may have been a fake, but with the information he had, he did the right thing. It's almost impossible to tell the difference from 20+ feet away.
What bugs me is all the people on other sites saying "why didn't he shoot it out of his hand", "why didn't he shoot him in the leg", "should have tazed him". It's not hollywood