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


Police officers ride an escalator into a train station in Munich, Germany, on July 23, 2016.

Photographer: Michael Nagle/Bloomberg

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. 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. Which recent attacks were lone-wolf terrorism?

Absent the requisite political motivation, the teenage gunman who carried out the July 22 shooting rampage at a Munich shopping center won’t be thought of as a lone-wolf terrorist. Even if the driver of the truck that mowed down revelers in Nice, France, on July 14 had a political motivation (along with his personal grievances), he may have had help from others, which excludes him from most definitions of a lone wolf. The killer of 49 people at a nightclub in Orlando, Florida, on June 12 looks for now like a lone-wolf terrorist.

3. If not terrorism, what explains the rash of mass killings?

Researchers have found that mass attacks -- terrorism or otherwise -- can inspire copycats.

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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