Looks real enough and doesn’t have the orange muzzle tip that airsoft ones do. However, it’s not clear from the story what the imminent threat was. It didn’t mention he was pointing it at the officer or someone else.
Carrying a rifle or pellet gun should not be an immediate, shoot on sight, death warrant.
The police officer startled the kid when he drove up beside him shouting, and with his gun drawn. What follows is conjecture: the startled kid intended to show that the gun was simply a pellet gun and in the course of doing so pointed the barrel in the general direction of the officer. Officer Jumpy, who had shocked the kid, proceeds to empty his revolver into the kid's body.
If the kid was pointing something that looked like a real firearm in any fashion that resembles a threatening act it could be argued that the cop had good reason to be *very* concerned for his own safety and/or the safety of others.
Nor does it mention the distance between the two, availability of cover, and a few other potential factors affecting officer response. I agree that cops are too likely to shoot first.