It did and he wasn't. See for yourself: <iframe width="560" height="315" src="//www.youtube.com/embed/MQUW3Km01BM" frameborder="0" allowfullscreen></iframe>
If he didn't have a gun, he could have raced his car into a crowd. He could have hurled Molotov Cocktails. He could have thrown acid in their faces. He could have made pipe bombs in his bedroom. Chicago outlawed firearms for a few years and the murder rate did not go down. In this PC era, we refuse to institutionalize psychopaths. Lots of citizens owned firearms in the 20th century - the difference was, the government had few qualms about institutionalizing those it deemed too mentally ill and a possible threat to the welfare and safety of the citizenry.
"HOW RELEASE OF MENTAL PATIENTS BEGAN" This is a NYT article from 1984 that Mark Levin has posted at his site. Worth a read. http://www.nytimes.com/1984/10/30/science/how-release-of-mental-patients-began.html?pagewanted
I'll keep saying it until leftists get it through their thick skulls. If a obviously mentally ill kid like this can slip through the cracks of the system, then we have no system. When the police are told, hey, over there, crazy guy with intent to kill, and they go "investigate", walk away saying nothing to see here, then we have no system. If we cannot depend upon the authorities to stop a killer when the killer is pointed out to them, then we shouldn't be surprised when people say we should arm everyone. I don't believe arming everyone is the solution, but I'm not at all surprised that some people do given the fact that we can't depend on the police at all to do what should have been a no brainer.