It would be wonderful to be able to predict and prevent mass shootings such as those that occurred in Jacksonville, Florida, Aurora, Colorado, Las Vegas, Sandy Hook, Connecticut, Parkland, Florida and elsewhere. But as much as people want to think that criminal investigations, trials, psychologists and psychiatrists can lead us to prevention, or determine a straightforward “why” for most mass killings and their perpetrators, they can't.
There is no "magic bullet" for identifying future mass killers, and certainly not one associated with my specialty of psychiatry. The difficulty is that, as much as we can describe the traits that most mass killers have in common, they aren’t useful as predictive tools.
For instance, almost all of those who have killed large numbers of people are males. Over half (in the U.S. and Canada) are Caucasian. Half or more have a diagnosable mental disorder. Close to 100 percent eat meat.
I'm not trying to be cute; I'm making an important point. It makes sense to look for factors, such as a recent history of severe violence, that contribute significantly to individual risk, but it is illogical to point the arrow of causation backward toward large population groups. Millions of times more mentally ill North Americans don't commit mass killings than do.
It is inaccurate and patently unfair to the 20 million or so diagnosably mentally ill people in North America to suggest that mental illness per se is at the root of mass killing — or any killing except suicide, for that matter. Very large and well-designed studies show over and over that the presence of mental illness in itself (excepting substance abuse) is neither a predictor of nor risk factor for violence, and certainly not lethal violence. I am far more worried about potential harm from "ordinary" criminals, abusive spouses, people impaired by alcohol, amphetamine and heroin abusers and sleepy drivers.....