After spending the past decade interviewing experts, analyzing Dylan's journals, talking with my family members, revisiting the days and years leading up to Columbine and working with others in suicide prevention, I realize there were signs, however unclear, that I might have recognized, knowing what I know now. But it was only after my son took part in what at the time was the worst school shooting in history that I — or anyone else close to Dylan — had any idea that there was anything wrong with him. Before Columbine, I would have told you with absolute certainty that I would know if there were anything amiss with my son, and even more so if anything were seriously wrong. But that raises an important question with regard to gun violence: If there are no flashing neon signs to alert us when someone needs help, how can we know who is and who is not mentally stable enough to be responsibly armed?