EXPERT: What Makes a Mass Killer?

Feb. 13, 2007 — -- Twice in 24 hours, a man brought a gun into a neutral situation -- a Salt Lake City shopping mall and a business meeting in Philadelphia -- and created a bloodbath. Besides the carnage, do these incidents share any similarities? What triggered this behavior? Do the gunmen have anything in common? And are there any behavior patterns that could identify these attackers before they strike? ABC NEWS.com asked ABC News consultant Dr. Michael Welner, a forensic psychiatrist and chairman of the Forensic Panel, to explain.

Cases such as the Philadelphia and Salt Lake City tragedies are often referred to as mass shootings. Why is that?

Because, from a forensic psychiatry standpoint, you have to consider that the mind-set of the person who carries out such an attack is the same, whether the attack kills or whether bullets merely fly.

The difference between a multiple homicide and a single homicide may be affected only, in these cases, by how accurate a shot someone is, or how fortunate a victim was that bullets did not mortally wound them.

I recall examining a mass shooter in Pittsburgh where the perpetrator killed three victims but shot two others in the head, who survived. To not group victims in such a spree together, simply when only one dies, is naive. Mass shooting covers the motive and speaks to the modus operandi and the leads that need to be understood by forensic scientists.

When we read about mass shootings, we hear that the people responsible are alienated loners. Is that all there is?

There are many alienated loners. Most don't kill. Nevertheless, mass shooters would not kill were they not to be so isolated, or so alienated. Depending on the setting, or the target, there are specific key ingredients to their personality, mood, life stage, triggers to the event, and sense of identity that combine, in the alienated loner, to a homicidal end.

How would a forensic psychiatrist differentiate between the Philadelphia mass shooting and the Salt Lake City mass shooting?

The Philadelphia mass shooting involved a workplace, financial interest setting; the Salt Lake City mass shooting involved a community shooting. In workplace settings, the killer feels emasculated by the target institution. He shoots to have the last word, by destroying the institution.

Not uncommonly, such shootings claim directors or presidents of target organizations, and victims who happen to be in close proximity to the killer. Even when a manager escapes, he may have been the primary target. Workplace mass shooters do not proceed beyond the boundaries of the office or chosen location to target random victims.

On the other hand, community shootings, such as the Salt Lake City case, do not involve a primary target or institution. The shooting may begin with someone the killer feels provoked him, or is symbolic of some perceived grudge. However, community mass shootings reflect someone with a substantial degree of paranoia and more general resentment toward the outside world. That paranoia may be a general suspiciousness and contempt of others or a full-blown delusional thinking.