GUN CRAZY:

Terrorism researchers emphasize that there is no single path that leads to mass murder, and the motivations behind such attacks are often a mix of the political and personal. In a 2010 paper, Australian sociologist Ramón Spaaij reported that "lone-wolf terrorists tend to create their own ideologies that combine personal frustrations and aversion with broader political, social, or religious aims."

In a 2014 paper that asks "What moves an individual from radical opinion to radical action," Bryn Mawr University researchers Clark McCauley and Sophia Moskalenko write that there are "at least two profiles for lone-wolf terrorists."

"Statistical studies indicate that may be called a disconnected-disordered profile: Individuals with a grievance and weapons experience who are socially disconnected and stressed with a psychological disorder," they write, while others "have a caring-consistency profile: They felt strongly the suffering of others and a personal responsibility to reduce or revenge this suffering."

McCauley and Moskalenko suspect the first group is more common, "not least because self-sacrifice for others is less common than self-interest." But perhaps because such people fit the stereotype of the dangerous loner, it's arguable that we pay insufficient attention to those in the second category.

McCauley and Moskalenko "emphasize the practical, situational requirements for crossing the gap between radical opinion and radical action." They argue that "the most dangerous indicator of potential for lone-wolf terrorism is the combination of radical opinion with means and opportunity for violent action."

To put it plainly: If terrorists were not able to get their hands on guns, ammunition, bomb-making equipment, and the like, they would not be able to act on their violent impulses.

Aside from the issue of tighter restrictions on firearms, the other question that always arises after such tragedies is the state of the perpetrator's mental health. Indeed, in his look at lone-wolf terrorists, Spaaij finds high rates of "psychological disturbance."

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