Psychologist Peter Langman wrote the book Why Kids Kill and says it’s common for shooters to want to study others, but there’s no one reason for killing

The Munich teenage shooter who killed nine people and injured 27 in a mass shooting in Germany on Friday appears to have fit a pattern among other mass murderers who researched shootings, according to the psychologist whose book was found in the gunman’s home.

“It’s a little disturbing,” said Peter Langman, who was unaware that the Munich shooter had a copy of his book until the Guardian called him at his home in Pennsylvania on Saturday. “I don’t know quite what to make of it. I don’t know why he had it,” he said.

The Munich shooter, whom local residents have named as a “lazy” German of Iranian ancestry, may have been trying to figure out his own thoughts, the psychologist said. “There must be some desire for self-understanding,” said Langman, who has spent decades studying the psychology of school shooters, has written several books and maintains an online research archive on school shooters.

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The gunman also apparently hacked a Facebook page and tried to lure victims to the McDonald’s where the shooting began with an offer of free food, according to German officials. He was still in school full-time, and had probably been in psychiatric care, with indications he was treated for depression, the police officials added.

“It’s common for shooters to want to study other shooters,” Langman said. The Sandy Hook shooter who killed 20 children and six adults in 2012, for instance, kept a spreadsheet of 500 mass murders, with explicit details about the attacks.

“They’re having thoughts of doing this and want to read about other people who did this,” Langman said of past shooters. “Whether that’s to find inspiration – I hate to use the word, inspiration – or a role model, someone to emulate, it’s hard to say.”

“Why they do that? I’m not sure,” he added. “Perhaps their own fascination, wanting to be the next big killer, they might want to affiliate themselves with other people who have achieved fame. For some, fame does seem to be a factor.”

One classmate told the Guardian that the gunman had been bullied, and seemed to have few friends. Investigators said that they had found no link to religious extremism or Islamic State, andthe police spokesman Peter Beck said officials “don’t yet know what triggered the crime”.

Langman downplayed bullying as a factor in mass violence at schools, however. “The bullying is much less a factor than people make it out to be,” he said, noting that bullies were rarely victims of attacks – and acknowledging that bullying was so common that its influence was difficult to measure.

“The fact someone has [been] teased doesn’t distinguish them from anyone else in middle school and high school. It’s not a defining characteristic – it’s more normal,” he said.



Much more powerful factors, he said, were mental health problems, school discipline, dysfunctional or abusive home life and even romantic rejection. “To focus on bullying misses so many other factors,” he said.

Langman’s 2010 book, Why Kids Kill: Inside the Minds of School Shooters, profiles 10 shooters and breaks them down into three personality types: psychopathic, psychotic and traumatized shooters. He says in his research that both US and international school shooters can be broken down into these three groups.

The Munich gunman was not the first to have been been found with a copy of Why Kids Kill. The book was also found in the possession of Karl Pierson, an 18-year-old who shot a fellow student and himself at a Colorado high school in 2013.

Pierson wrote in his diary that he was psychopathic with a superiority complex. “I think he was right and correctly identified himself as a psychopathic personality from my book,” Langman said.

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Langman said he tried to be very careful not to provide any guidance for prospective shooters; his book is intended for parents, counsellors and psychologists.

“That’s something I stay away from completely,” he said. “The whole point is to prevent shooters, not to give people tips. There’s a chapter on warning signs and prevention.”

The psychologist added that he shied away from graphic details about the murderers, guns involved or any videos or photos or the killers or victims.

“I don’t talk about technique or strategy, I stay away from all the gory details,” said Langman. “That’s not my purpose. As a psychologist, I’m trying to get inside their mind to understand what put them on the path of violence and what are the warning signs so we can stop people on the path of violence.”

And why, as his book title asks, do kids kill?

“There’s no one reason, and I think people are often looking for the one-word answer,” Langman said. He noted that some attacks were directed against victims the shooters has a specific grievance with, such as a girl who rejected them or a teacher who disciplined them. Others attack randomly; their victims are strangers.

“Sometimes there’s a revenge factor. Sometimes they are full of rage and lashing out against the world,” he said. “Sometimes they are wanting to make a name for themselves. As a nobody, they see the only way to be a somebody is get international recognition for killing people.”