“It was very, very rare for the primary motive to be political, though there were a number of attackers who appeared to clothe their motives with some political rhetoric,” Fein says.

What emerges from the study is that rather than being politically motivated, many of the assassins and would-be assassins simply felt invisible. In the year before their attacks, most struggled with acute reversals and disappointment in their lives, which, the paper argues, was the true motive. They didn’t want to see themselves as nonentities.

“They experienced failure after failure after failure, and decided that rather than being a ‘nobody,’ they wanted to be a ‘somebody,’ ” Fein says.

They chose political targets, then, because political targets were a sure way to transform this situation: They would be known.