Predicting the Future, Disarming Bad People

BY NOW,we are all all too familiar with the new american tradition whereby somebody walks, heavily armed, into a public place, and kills as many people as possible in the short time available. Then, the media takes over, the gun control debate heats up, and we all agree that the answer is to keep guns out of the hands of "bad people", and out of the hands of people who are mentally ill. Then comes the hard part; deciding who the bad people and the mentally ill people are, and disarming them, before they strike. The impossible part is predicting the future. We start to learn that the line between good and bad, between mentally healthy and mentally ill, can become a bit blurry. For instance, I happen to know a fifteen year old kid who, in my opinion, is a borderline psychopath, mentally disabled AND mentally ill, and, at some point in the future, as he approaches adulthood, likely to inflict violence on someone. I see this kid every day, and have for the past two and a half years, and feel that I know what I am talking about. He is currently on probation for throwing a chair at another kid at school. Nothing that he has done so far would prevent him, at the age of eighteen, from legally owning a firearm. But this guy should never be allowed to get within a ten foot pole of a firearm. So what is my responsibility here? What should I do? Notify the FBI? The NSA? Talk to the local police? Would any of that accomplish anything? Or would I be told that there is nothing that can be done, because nothing has happened, and there is no legal ground to deprive a minor of a constitutaional right he will have as an adult, if he stays out of any big trouble in the meantime? What you any good american citizen do upon encountering a person who, in the best judgment of said american citizen, was a potential mass murderer, due to mental instability? Are we all, as citizens, obligated to alert someone, some proper authority, mental health professional, law enforcement agency, someone, anyone, when we know someone who is quite obviously capable of and likely to behave violently in the future? If we ever get to the point where we, as citizens, are being strongly encouraged to report anyone who we think fits this description, the list might become very long. We might all end up on the "no gun" list. then we would have the unthinkable situation of living in a disarmed nation, in which all of us good mentally healthy people are gunless, becasue of some busy body neighbor or friend. Wouldn't that be horrible!