Trump attempted shooting: what drives a solo assassin to kill? A psychologist explains

The image of the would-be assassin at Donald Trump’s rally in Butler, Pennsylvania, on July 13 is now part of history. A young man in beige lying dead on the flat roof. Minutes earlier, this self-appointed executioner had been pointing his rifle at Trump, aiming to shoot the former president in front of his followers.

What drove this young man to try to kill? Thomas Matthew Crooks was 20 years old, two years out of school and still living with his parents in a town an hour away from the shooting. In his 2022 school yearbook photos, Crooks bears little resemblance to the assassins of film and television who are typically hardened, self-reliant executioners or highly professional hitmen or women.

As far his marksmanship goes, former classmates said Crooks had been rejected from the school rifle team because he was a terrible shot. But coldblooded killers come in all shapes and sizes, as I discovered when I interviewed a number of killers from the streets of Belfast for my 2005 book, Protestant Boy.

These killers, caught up in the Troubles in Northern Ireland, belonged to various paramilitary organisations. They had organisational and social support, and ideologies that allowed them to justify their acts – even the murders of completely innocent civilians.

Belonging to a paramilitary organisation allowed them to build a shared narrative: “The state do even worse things than us,” they would say indignantly, “with the SAS and their shoot-to-kill policy.”

Lone wolf

In contrast, so-called lone-wolf assassins have no group like this to fall back on, to share and dilute responsibility for their actions. They’re on their own, without the protection of a socially-shared narrative.

Psychological research reinforces this notion of difference. American researcher Clark McCauley and colleagues have suggested that mental disorder is particularly prevalent in lone-wolf terrorists. Theodore Kaczynski, the “Unabomber”, was diagnosed with paranoid schizophrenia.

Jared Loughner, who shot and severely injured US congresswoman Gabby Giffords and killed six others in 2011, was schizophrenic. Anders Breivik, the Norwegian neo-Nazi who killed 77 people the same year, was originally also thought to suffer from schizophrenia, but his diagnosis was subsequently changed to narcissistic personality disorder.

In 2015, psychologists Emily Corner and Paul Gill conducted an analysis of 119 lone-actor terrorists and a matched sample of group-based terrorists, and found the probability of a lone-actor terrorist having a mental illness was 13.5 times higher than a group-based terrorist.

But while some form of mental disorder may be a risk factor for lone-wolf terrorism, there are additional factors which seem to be critical. These include holding a strong personal or political grievance, coupled with some form of desensitisation to violence through a gradual escalation of violent behaviour.

The story of Mark Chapman, John Lennon’s killer, suggests that status-seeking can also be important. This may be even more prevalent now in our social media-dominated world, coinciding with what some psychologists suggest is a dramatic rise in narcissism and narcissistic personality disorder.

A photo of Thomas Matthew Crooks aged about 18, taken from his 2022 school yearbook. CBS news

When this narcissism is combined with lack of empathy, callousness and emotional flatness of the kind you tend to find in psychopathy, then you can have a particularly dangerous combination.

What drives an assassin?

How prevalent are these factors among assassins? A 1999 report by US psychologist Robert Fein and Bryan Vossekuil, then executive director of the National Threat Assessment Center with the US secret service, analysed all people who attacked, or approached to attack, a “prominent person of public status in the US since 1949”. There were 83 assassins analysed: most (86%) were male, the vast majority (77%) were Caucasian, and more than half (55%) had seen service in the military.

In their 2013 article, which looked at data from the Fein-Vossekuil report, McCauley and colleagues, , suggested that grievance is indeed a significant factor for assassins (67%). In 71% of cases, a prior history of weapon use was also identified, and in 59% a history of interest in violence. Some 44% of the assassins studied by Fein and Vossekuil were found to have had suicidal thoughts or had attempted suicide.

While different assassins and lone-wolf terrorists clearly act on a range of different motives, there appear to be common elements: some sort of mental disturbance; a festering grievance vented in echo chambers on the internet, or bottled up inside but rarely properly articulated. There is also, generally, an interest in violence combined with desensitisation to that violence, and a desire to raise their social status through any means.

Crooks only succeeded in injuring Trump, so if he set out to kill the former president, he failed in his objective. But we all know his name now, and that might well have been very important to him.