Nope. He could have just as easily gotten pissed off and shot the place up. Nothing the cops could have done. It would have been a bloodbath. But what has been suggested (including by you), is that he did nothing wrong. Not one thing. That he posed no threat, and the fact he had an arsenal in his car was just him, what, being ready to go hunting after his visit to the CIA and his stop at a preschool? Okay, you go with that. I see a problem. But that's just me I guess.
Oh, wait, the answer is obvious. Arm the three year olds. Why didn't I thnk of that
Again, imagination makes every thing scary to Concart.
He "could have" tried to flap his arms and poop an egg too. The list of things he "could have" but "didn't" do is infinite, and still imaginary.
Your fictional accounts of "what ifs" are not a sound basis for a form of government or even for a form of news.