QuickTake Q&A: Accounting for the Rise of Lone-Wolf Terrorists


A mass killer, acting alone, strikes in the name of a political cause but without belonging to an organized movement. A disturbed criminal, or a committed terrorist? Security scholars put such murderers in a middle category: the lone-wolf terrorist. The phenomenon isn’t new. But one of the great worries of security officials across the globe is that social media and the active encouragement by groups like Islamic State may be making for a surge in these hard-to-stop killers.

1. What is a lone-wolf terrorist?

Differing definitions coalesce around these criteria: the perpetrator acts alone and without specific instructions; is politically motivated; and has no formal ties to an organization. So the husband and wife who killed 14 in San Bernardino, California, in 2015, generally aren’t thought to have been lone wolves. Nor is Adam Lanza, who killed 26 people at a school in Newtown, Connecticut, in 2012, and seems to have had only a personal motive. Experts say lone wolves tend to harbor both personal and political grievances. More often than not, they display signs of mental instability. One study found that lone wolves are 13.5 times more likely to have a mental illness than a terrorist acting within a group.

2. Was the attacker in Munich a lone-wolf terrorist?

So far the evidence suggests he was not. The rampage at a Munich shopping center on July 22 was staged by a teenage gunman who was acting alone and without political motivation, police said. A search of his home yielded no evidence of any link to terrorism but showed that he had studied past shootings. Newspaper articles and a book about school shootings found in his bedroom suggested interest in such incidents. Germany has so far been spared the type of terrorist attacks that killed hundreds in Paris, Nice and Brussels, though the authorities have repeatedly warned that the threat remains high. Tensions have risen since mass sexual assaults in Cologne and other cities on New Year’s Eve and an attack on Monday near the Bavarian town of Treuchtlingen in which two people were critically injured with an ax on a train by a 17-year-old Afghan refugee.

3. Was the Nice, France, killer a lone-wolf terrorist?

Islamic State claimed the attack was carried out by one of its "soldiers," but French authorities have said they have no evidence Mohamed Lahouaiej Bouhlel, who was killed by police, was tied to the group. French officials say Bouhlel got help from at least five people, but there’s no evidence they had direct contact with Islamic State, according to the New York Times.

4. How common are lone-wolf terrorist attacks?

A study of 5,646 terrorist attacks around the world from 1968 to 2010 found that 72, or 1.3 percent of them, were committed by lone wolves. In recent decades, such attacks became more frequent in the U.S. The study was conducted before Islamic State leaders in 2014 began to urge followers to do whatever they could to kill citizens of nations fighting the group. A 2015 study funded by the U.S. Department of Justice found that lone-wolf attacks in the U.S. became more common after the terror attacks of Sept. 11, 2001.

5. What special challenges do lone-wolf terrorists present?

Because lone wolves don’t belong to organizations that can be infiltrated and monitored, they are difficult to detect and stop. This is why two white supremacists, Tom Metzger and Alex Curtis, advocated "lone wolf" actions among their fellow believers in the 1990s, pushing the term into the mainstream. However, most lone-wolf attackers in the U.S. have broadcast their violent intentions in advance, in statements to associates, on social media or in various forms of protest. That provides an opportunity for law enforcement to find lone wolves before they act.

The Reference Shelf

  • A Bloomberg View opinion piece on lone-wolf attacks.
  • A study on lone-wolf terrorism in America.
  • A study on the connection between mental illness and lone-actor terrorism.
  • A QuickTake explainer on the July 14 attack in Nice, France.
  • An article comparing lone wolves to assassins and school attackers.

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