Is It Possible to Stop Terrorists Who Act Alone?

On New Year’s Day, a lone driver sped a rented pickup truck into a crowd celebrating along crowded Bourbon Street in New Orleans. The attacker is believed to have acted alone, despite posting online about his support for the Islamic State. In 2022, a white supremacist opened fire in a supermarket in Buffalo, N.Y., targeting Black customers. Although motivated by racist conspiracy theories he found online, he acted alone.

For law enforcement, detecting and thwarting these mass-casualty attacks from lone actors can be particularly challenging. Police have strategies for reducing or responding to such threats, but they cannot do it alone. Experts suggest that information from the public, improved mental health services and other supports could be an important part of addressing lone wolf terrorism.

“The very nature of those lone attackers, or lone wolves, is that they don’t necessarily make themselves known,” says Chuck Wexler, executive director of the Police Executive Research Forum. “Predicting an individual who is engaged in that activity, who is not associated with others, is very challenging, and the best police can do is try to be prepared.”

These lone attackers typically align themselves with a cause and often are radicalized through content they consume online. Or, if they’re radicalized by a local group, they typically look online for more information and to learn attack strategies, says David Viola, adjunct professor at the Center on Terrorism at John Jay College of Criminal Justice. Monitoring extremist conversations on social media and looking for which users are discussing violence can offer indicators.

Still, Viola notes, it’s a hefty lift for law enforcement to sort through the sea of content online for genuine threats, and they must be careful to avoid infringing on civil rights or profiling people. Studies also show that far more people say they find certain ideology-driven violence justified than ever actually try to commit it.

Understanding Lone Wolves

The U.S. has a long history of lone wolf terrorism, but these kinds of attacks have been evolving. The easy availability of powerful guns is a major reason lone wolf attacks have so many victims, Viola says. Guns are a more accessible and reliable weapon than homemade bombs, which sometimes explode on the people making them. “If I did a list of the 10 deadliest terrorist attacks since 9/11 in the United States of America, I would venture a guess that eight of them would involve high-powered firearms,” Viola says.

But attacks don’t require guns, with vehicle-based attacks happening more frequently. Terrorists learn from seeing what others do; the recent New Orleans attacker is known to have researched a December 2024 attack in Germany that used similar car-ramming tactics and may also have been inspired by the truck attacks in 2016 in Nice, France, and 2017 in New York City. “Some Americans don't know how to shoot a gun,” Viola says. “But the vast majority of Americans know how to drive a pickup truck.”

Terrorism is violent political expression and the U.S. could better deter such attacks by promoting moderate voices who speak to the same communities and present alternatives to extremism. The U.S. also needs to work to tackle online misinformation and conspiracy theories, which can also spur people to violence, Viola says. But the trend among social media giants lately is to reduce content moderation.

There’s no single profile of a lone wolf attacker, and individual cases can defy the norms. But radicalizing factors can include feeling socially alienated, lacking meaning or feeling untethered, says Sophia Moskalenko, co-author of the book Radicalization to Terrorism: What Everyone Needs to Know. She also finds there is a significantly greater prevalence of mental illness among people who become lone wolf attackers, compared to the general population or even group-based terrorists.

Mental health conditions alone don’t cause radicalization. But suffering certain disorders such as substance abuse, schizophrenia, bipolar disorder, schizoid and other personality disorders, which blur the lines between thoughts and reality, may make people more susceptible when combined with other factors. People who are immersed, day in and day out, in an online environment full of conspiracy theories and other radicalizing materials and narratives, while also suffering such disorders, are more likely to feel like they need to take actions in response. “That online narrative becomes their reality and they cannot regulate their thought processes and their behaviors in response to it,” Moskalenko says.

Although PTSD does not make someone likely to become radicalized, she says, it can contribute to the tendency because it impairs impulse control and emotional regulation and leads to obsessive thoughts. As a result, people who are in a radicalizing social media environment who also have PTSD may be more prone to turning to real-world violence, Moskalenko says. “The mental health services is our best line of defense against this kind of radicalization,” she says.

Hardening Targets

Police can defend some large outdoor gatherings with physical barriers, such as bollards that protect against vehicular attacks. It’s not just the type of defense that matters, but its quality. Wexler, of the Police Executive Research Forum, notes some bollards will only stop a car going 10 mph, while others could withstand a heavy vehicle like a truck. New Orleans reportedly ran into issues with debris like Mardi Gras beads jamming the mechanisms for temporarily deploying bollards.

But Viola, the John Jay professor, notes that “it's impossible to harden every site that terrorists might think is an opportunity.” And, while police will likely set up multiple perimeters to tightly secure a major event such as the Super Bowl, there will also be many festivities in the days leading up to it that could be at risk, Wexler says.

Today’s cities have many surveillance cameras, which can help with quickly finding perpetrators if something does happen. Police may also find it helpful to look for members of the crowd who don’t seem to belong, because of how they dress or act. For example, footage showed the Boston Marathon bombers moving through the crowds without stopping to watch the race, Wexler says.

There’s a reason we still hear announcements reminding us that if we see something to say something: Important information on lone wolf attackers can come from the public. Bystanders may spot something unusual in a public space and report it to an officer, such as an abandoned bag or a person acting suspicious. Family or friends may learn of a would-be attackers’ plans and report it.

When police receive calls of concern about a person, especially someone with a track record, they need to take it seriously, Wexler says. But short staffing at some police departments makes it difficult to investigate all leads.