So assuming I picked the correct result, and the story in question is regarding one Andrew Lopez, here are the salient details: the "plastic toy gun" was a replica assault rifle of considerable realism, and Lopez was repeatedly ordered to drop the "weapon" but failed to comply.
That alone tells me this case doesn't at all support the claim that "the police will kill on sight".
Or did I perhaps pick the wrong google result? Maybe Elusis' snide "Let Me Google That For You" link doesn't actually properly lead to the case that rattypilgrim meant? If so, I'll gladly accept an actual citation from the person actually making the argument.
Until such time, I am well within rationality to dismiss the argument wholesale for lacking any relevant, verifiable evidence to support it at all. Burden of proof and all that.