The plane that crashed, apparently deliberately, into an Austin, Texas, office building that housed offices of the Internal Revenue Service shocked the community and the nation, but may not have been an isolated incident. Instead, the crash may have been the latest in a series of acts of "lone wolf" violence that have plagued the United States in the last 15 months.

"Lone wolf" terrorists are individual extremists who commit violent acts on their own without belonging to an organized extremist or terrorist group or cell. Such a description may well fit Joseph Stack, the man suspected of having deliberately piloted the plane into the Echelon Building on February 18, 2010.

In an on-line manifesto believed to have been written by Stack in the days before the incident and posted to his Web site just hours before the crash, an intense hatred of the government and a desire for violence is clear. Most of the anger in the manifesto is directed at the U.S. government; in particular, at the IRS. In the manifesto, Stack expresses a sentiment common to many domestic extremists, that "the American zombies wake up and revolt." Stack allegedly hoped that his action would cause a "standard, knee-jerk government reaction that results in more stupid draconian restrictions," which in turn would cause people to "wake up." Violence, Stack allegedly wrote, "not only is the answer, it is the only answer."

Howls of the Lone Wolves

Stack's deadly conclusion, that violence was the "only answer," is a conclusion that others have also unfortunately arrived at in recent months. Their ranks have included extremists from many backgrounds: white supremacists, Muslim extremists, anti-abortion extremists, and others. More than 30 extremist related killings occurred in the United States in 2009 alone. Of these, a number bore the hallmarks of "lone wolf" attacks, including the following deadly incidents:

• November 2009, Fort Hood, Texas. Army Major Nidal Malik Hasan, seemingly motivated by anger over U.S. involvement in Iraq and Afghanistan, opens fire at a readiness center, killing 13 and injuring dozens more.
• June 2009, Washington, D.C. White supremacist James Von Brunn opened fire inside the U.S. Holocaust Memorial Museum, killing a security guard before being critically injured by return fire from another guard.
• June 2009, Little Rock, Arkansas. Abdulhakim Muhammad was arrested for shooting two American soldiers, killing one, at a military recruiting center, allegedly "because of what they had done to Muslims in the past."
• May 2009, Wichita, Kansas. Anti-abortion extremist and sovereign citizen Scott Roeder fatally shot a physician whose clinic provided abortions, while the physician was acting as an usher at his church.
• April 2009, Pittsburgh, Pennsylvania. White supremacist Richard Poplawski was arrested for allegedly ambushing and killing three Pittsburgh police officers.
• January 2009, Brockton, Massachusetts. White supremacist Keith Luke embarked on a racially motivated shooting and violence spree, allegedly killing two West African immigrants (and shooting and raping a third). Police stopped him before he could carry out his alleged final act, opening fire inside a crowded synagogue.

Though this is not always reported by the media, most terrorist plots and conspiracies that occur in the United States are detected and prevented by law enforcement officers before their planned acts of violence can be carried out. "Lone wolves," though, are feared precisely because their acts are so difficult to prevent. When extremists work alone, not belonging to groups or cells, there are far fewer opportunities to detect them in advance. Some such individuals, such as Ted Kaczynski, better known as the "Unabomber," and Eric Rudolph, have been able to carry out multiple terrorist acts before being caught.

Moreover, "lone wolf" actions tend to be very deadly, as causing human casualties is usually the prime goal of the perpetrator. "Lone wolf" actions are, in this sense, ideologically-driven cousins to certain other types of violence, such as shooting sprees by disgruntled former employees or former spouses.

The most common instrument of "lone wolf" violence is a shooting or shooting spree, with bombings coming in a distant second. Other types of violence are also sometimes seen. Stack, who allegedly flew a plane into a building housing government employees, was not even the first "lone wolf" to employ this tactic; a troubled teen in Florida, Charles Bishop, flew a small plane into a Tampa skyscraper in 2002, allegedly inspired by Osama Bin Laden and the 9/11 attacks. Like Stack, Bishop had no known connection to organized groups or movements.

Profiling Lone Wolves

Analysis of "lone wolf" incidents over the past 20 years reveals several patterns and dynamics common among "lone wolf" offenders that can be used to create rough profiles.

• Gender and Age. Although "lone wolf" offenders have tended overwhelmingly to be male, they have ranged greatly in age from teens to senior citizens. Many, however, seem to fall into one of two clumps: 1) males in their early to mid-20s and 2) middle-aged males.
• Lack of Direct Incitement. Over the years, extremists have emerged from various movements as proponents of "lone wolf" attacks, trying implicitly or explicitly to encourage people to engage in violence on their own, rather than as part of a group action. White supremacists in particular, including Louis Beam, Thomas Metzger, and Alex Curtis, among others have repeatedly advocated variations on this tactic. However, they seem to have had little success. Most "lone wolves" who embark on violence do not seem to have deliberately chosen a "leaderless resistance" tactic as a conscious choice. Rather, other factors (see below) played the key roles in their decision-making process.
• Isolation. Many "lone wolves" seem to act on their own not so much as a deliberate choice but at least as much because they "don't play well with others." Some tend to have loner personalities, while others may have characteristics or behaviors which would cause others to tend to shun or avoid them.
• Peripheral Status. It is not uncommon for a "lone wolf" to be part of an extremist movement, but when they do so, they usually are at the periphery of the movement rather than at its core. They may occasionally attend an extremist event or rally, but will rarely join groups. Sometimes a "lone wolf" may flirt with joining a group or even start an abortive group of their own, but they typically don't stick with it. Richard Baumhammers, a white supremacist who went on a murderous spree targeting religious and ethnic minorities in Pittsburgh in 2000, was an example of this sort of peripheral figure who halfheartedly tried to start his own group.

  In some cases, "lone wolf" perpetrators may not even be on the periphery of a movement, but may have an ideology that is more self-formed than imbibed from others; in such cases, they may essentially "self-radicalize." Stack himself may well have fallen into this category. Although some of the language in his manifesto suggests he may have had some involvement with the tax protest movement in the early 1980s, most of the sentiments expressed do not fit neatly within an established ideological movement, and may have been largely self-formed.

• Spontaneous vs. Planned Incidents. Some "lone wolves" may exist for some time in a highly agitated state, only to be set off by some specific incident and engage in spontaneous violence. It is more common, however, for the violence to have been preceded by days to weeks of brooding, fantasizing, or planning. Keith Luke allegedly repeatedly watched white supremacist videos in the days before his killing spree; even Richard Poplawski, whose violence consisted of an alleged ambush, had reportedly talked about a hit list of sorts.
• Personal Stresses. Many "lone wolves" feel intense personal stresses that may in fact be entirely separate from their ideological or political beliefs. The stresses could be financial in nature, such as being laid off, or possibly familial, such as marital problems. In some cases, the presence of ideological or political beliefs may guide the "lone wolf" towards related targets. In 2002, for example, Hesham Mohamed Hadayet, an Egyptian citizen, opened fire at the El Al ticket counter at the Los Angeles International Airport, killing two and wounding four before being killed by a security guard. Hadayet was suffering from considerable personal stress: his business was in trouble, his marriage was in trouble, and he was depressed and alone. However, when he chose a target to act out against, he chose an Israeli target because of his ideological views.
• Mental Illness. In some cases, "lone wolf" perpetrators may suffer from some form of mental illness or instability that may possibly have contributed to the decision to become violent. Richard Baumhammers had a history of mental illness; so too allegedly did Keith Luke.

Mitigating Lone Wolf Violence

Unfortunately, there are no easy ways to prevent "lone wolf" violence in advance. Sometimes friends or relatives may spot signs of intense stress that suggest a possibility for violence and may even contact the authorities over such signs; police should always take such warnings seriously. Occasionally, even people in an extremist movement may warn others in the movement to stay away from someone who seems dangerous and unpredictable to them.

However vigilant people may be, though, they cannot eliminate the chances of "lone wolf" violence. However, law enforcement agencies may possibly reduce the casualties that can result from such an incident by actively training their officers in "active shooter" response tactics; such tactics can save many lives.