In the wake of a terrible tragedy such as the elementary school massacre in Newtown, Conn., people immediately grope for answers.

On Sunday, a family member claimed that Nancy Lanza, mother of 20-year-old gunman Adam Lanza, owned the guns used in the shooting because she was some manner of survivalist. The reasons Adam Lanza did what he did may well be complex. But if the report proves to be true - and many, many reports about the Lanzas have not - it may provide context for his actions.

Survivalism, sometimes referred to as "doomsday prepping," or simply "prepping," is a movement based on the fear that society is on the brink of collapse and that it's sensible to prepare for that possibility.

"Survivalist" is a very broad category, and it includes a strikingly diverse collection of people, many of whom, it should be emphasized, are perfectly nice and have fears that are simply amplified versions of those that keep mainstream Americans awake at night. There are at least tens of thousands of prepper families in the United States, covering a broad range of practices, most of which are not particularly unreasonable.

Someone who closely followed the preparedness guidelines issued by the Department of Homeland Security, the Centers for Disease Control or FEMA might find themselves the butt of jokes from their friends and family. But those friends would have been grateful to have a prepper friend if they lived in certain parts of the East Coast when Hurricane Sandy struck.

Preppers go beyond the average household's disaster preparedness regime of having flashlight batteries on hand. Their precautions include everything from stockpiling canned goods to buying generators and building elaborate bunkers. Many keep guns and a supply of ammunition in anticipation of the breakdown of law and order, as well as for hunting after the local Whole Foods has been abandoned to looters.

Shortly after press reports about Nancy Lanza's alleged survivalism appeared, the American Preppers Network issued a statement, which said: "Our members, and others around the globe who share our philosophy of being prepared in times of emergency, are sickened by this event. We too are fathers, mothers, brothers, sisters, sons and daughters, and to associate APN or any legitimate organization that stresses preparing for emergencies with this barbaric act goes against everything we collectively stand for."

Despite this statement, which is generally correct, prepper subculture can go further than intensive or even excessive preparation. Most survivalism is based around fear of a sometimes ambiguous, sometimes specific disaster that is just around the corner. Because it can be anything from the collapse of the dollar to an electromagnetic pulse detonation to a race war, survivalist tendencies are sometimes - but not always - paired with malignant forms of extremism, such as ideological racism, sovereign citizenship, apocalyptic religion, or anti-government beliefs on both the right and the left sides of the political spectrum.

Timothy McVeigh and Terry Nichols, for instance, took part in survivalist subculture in addition to their anti-government ideology, and extensive sections of the white nationalist web forum Stormfront are dedicated to discussions of disaster. But survivalism tends to be an add-on to such ideologies, not a fundamental cause.

In addition, survivalism itself can lead to dangerous behavior. Most obviously, in the context of the Lanza family, someone who believes the government is on the verge of collapse might stockpile weapons and train his or her children to use them without taking a full inventory of that child's mental fitness.

There have been a number of cases where survivalism and violent actions were fellow travelers. The 1995 Olympic Park bomber, Eric Rudolph, was a survivalist, in addition to being an anti-abortion extremist. In 2004, police broke up an illegal weapons ring involving several militia and survival groups. And in April of this year, Washington state survivalist Peter Keller killed his wife and daughter and then locked himself into a fortified rural bunker, where he killed himself after a standoff with police. But evidence suggests that although Keller's preparations created obvious complications for police trying to apprehend him, his beliefs did not seem to play a role in his murderous acts.

Therein lies the rub. The term survivalist is often bandied about by police and reporters groping for a simple explanation of inaccessible motives.

The extremity of Adam Lanza's crime creates a desperate desire for explanations. Dismissing him as a crazy survivalist - or the son of a crazy survivalist - may prove irresistible for many people. But his motive is not likely to be so simple.

Additional information will emerge over the coming days, but we may never really know why Lanza killed his mother and so many innocent teachers and children. Understanding the context of his actions may provide useful insights that could prevent future incidents, but gross oversimplifications will only stand in the way.

J.M. Berger is editor of Intelwire.com and author of "Jihad Joe: Americans Who Go to War in the Name of Islam." He wrote this for Foreign Policy.