There are good reasons to prevent some users of psychiatric services, some of the time, from having access to weapons. This is different from saying that a “dangerous people” approach to gun ownership applied to a psychiatric population can be expected to prevent future outrages. Dr. Swanson is right, for many reasons, to suggest that services should be improved. But we don't know how much gun violence would thereby be prevented and, as a result, cannot assume that a further decline in the U.S. homicide rate would be a likely consequence. From a psychiatric standpoint, the strongest statement that can safely be made in relation to recent notorious incidents is that improved services might have prevented some of them. Research into risk assessment will continue to advance, but this will remain true. The difficulty is not attributable to a lack of data.