The idea that someone could suddenly snap and slaughter large numbers of people has become part of the understanding of events such as the Columbine school massacre and the D.C. Sniper case. But this image of the sudden turn from ordinary citizen, quiet neighbour, or non-descript teenager to mass murderer is generally false. People who go out one day and kill innocent people or supposed enemies have typically thought about it, planned it, and even mentioned it to others before they actually do it - and the act is usually the result of a build-up of stress and frustration. Katherine Ramsland, an experienced crime writer, examines true stories of mass murder and reveals the complexity behind the development of a mass killer. She provides examples of common signals, based on actual cases, that will help readers to identify warning signs and to understand the various psychological factors that may lead a person to kill. Recognizing these signs may help to defuse a potentially violent situation before it occurs. Using details from various cases, the author examines the different kinds of mass murders, from visionary to family to workplace, and the distinct psychological dynamics of the different types of murders. From the religious martyrs at Waco to the disgruntled teens at Columbine, this essential book exposes the inner world of mass murderers and dismantles the stereotypes we hold about them.