The HOPE Columbine Memorial Library that replaced the library where most of the massacre took place. (PHOTO: BIGMAC/WIKIMEDIA COMMONS)

In trying to understand the actions of a mass murderer, our instinct is to grasp blindly for answers, settling on one that feels right. Setting aside the debate over access to guns, this often comes down to a lay diagnosis that the shooter was probably a psychopath—cold, unfeeling, heartless.

A new analysis of the writings of three mass killers and one would-be mass killer, comes to a very different conclusion. A trio of University of British Columbia psychologists led by Donald Dutton report the gunmen appear to have suffered from an intense form of paranoia.

Far from being cool or detached, these young men were enraged, their delusions of persecution becoming ever more intense and intolerable.

“The paranoid individual is obsessed with revenge and justifies the revenge as payback for a perceived injustice. (Such people are) thin-skinned or hypersensitive to perceived slights.”

“They become and remain fixated and obsessed with rejection by what they see as an elite in-group, whom they see as having unfairly achieved success,” Dutton and his colleagues write in a compelling paper just published in the journal Aggression and Violent Behavior. “Instead of transcending the rejection, they formulate plans to annihilate the transgressors, which they justify as vengeance for the transgressions made against them.”

The researchers analyzed the writings of Eric Harris, who (along with friend Dylan Klebold) killed 13 of his fellow students at Columbine High School in 1999; Seung Hui Cho, who killed 32 people at Virginia Tech in 2007; Kimveer Gill, who shot 20 people, killing one, at Dawson College in Montreal in 2006; and Anders Breivik, who killed 82 people at a youth camp in Norway in 2011 (plus another seven in a bomb blast outside the Prime Minister’s office).

They looked at the perpetrators’ diaries or blog entries in the weeks leading up to the shooting, as well as a manifesto Breivik circulated in a mass email in an attempt to explain himself. Aside from Breivik, whose paranoia found expression in socio-political terms, they expressed a surprisingly similar worldview.

“A central theme that runs through these diaries is one of feeling rejected, dismissed, disrespected and devalued by an in-group invariably depicted as “jocks and preppies,” and of wanting vengeance for this maltreatment,” Dutton and his colleagues write. “The in-group is despised for being superficial and for getting unwanted status.”

There is no shortage of examples of this kind of thinking. This is from Harris’ diary:

Everyone is making fun of me because of how I look, how fucking weak I am, and shit, well I will get you all back, ultimate fucking revenge here. You people could have shown more respect, treated me better, asked for more knowledge or guidance more, treated me more like a senior, and maybe I wouldn’t have been so ready to tear your fucking heads off. ... Same thing with all those rich snotty toadies at my school. Fuckers think they are higher than me and everyone else with all their $ just because they were born into it?

Here is an online posting by Gill, translated from the French:

If people were making your life a living hell, wouldn’t you be hurt emotionally? How come no one ever talks about those mother fucking jocks and preps whose fault it is. Oh no. Heaven forbid. We can’t possibly say that. Why does society applaud jocks? I do not understand. They are the worst kind of people on earth. And the preps are no better. They think they’re better than others, but they’re not.

Finally, here’s Virginia Tech shooter Seung Hui Cho, apparently addressing the sort of privileged student he despises:

Your Mercedes wasn’t enough? Your golden necklaces weren’t enough? Your trust fund wasn’t enough? Your vodka and cognac weren’t enough? All your debaucheries weren’t enough?

“The paranoid individual is obsessed with revenge and justifies the revenge as payback for a perceived injustice,” the researchers write. “(Such people are) thin-skinned or hypersensitive to perceived slights (and they) have closed information-processing systems that preclude corrective information which is inconsistent with their world view from being received.”

Breivik, the oldest of this group (he was 32 at the time of the killings; Harris was 18, Cho 23, and Hill 25), perceived a different enemy: Muslims. His paranoia "appeared to have worsened when he was past college age,” the researchers write. “Otherwise, his school peers, rather than a politically derived target, may have been selected.”

“He believed that slaughtering a group of teenagers would make him Grand Master Knight Commander, deputized by a secret society to lead the forces of Christendom in a battle for the future of mankind,” they add. “He had military uniforms made to reflect his future status.”

Overall, this analysis suggests many of the media's cliches regarding mass killers appear to be wrong. They were bullied? “This group greatly exaggerates the negativity of their treatment, as reported by third-party school peers,” the researchers note, adding that their writings contain few references to specific experiences of being a bullying victim.

Perhaps the problem is too few mental health services? Well, three of the four men examined here had been assessed by psychiatrists, none of whom picked up on the deep nature of their disturbances.

That said, one popular conception about these men is clearly correct.

“There were differing levels of social isolation for Cho, Gill, Breivik and Harris,” the researchers write. “Cho had extreme social anxiety, isolated himself and showed social incompetence. Gill and Harris had some friends, but clearly pictured themselves as marginalized. “All were described as loners.”