The ECSP was a 5-year study that examined the thinking and behavior of individuals who have attacked or approached to attack prominent public officials or figures in the United States since 1949 (n=83). Although not intended as an operations manual, this guide presents information and ideas about developing and implementing protective intelligence programs and activities. Information about the thinking and behavior of persons who have attacked or come close to attacking public officials and figures can help refine law enforcement operations related to preventing and investigating violence and threats of violence. The primary goal of every protective intelligence investigation is to prevent an attack on a potential target. By using a combination of investigative skill, corroboration, and common sense, a protective intelligence investigator can gather the information and evidence to make an assessment of the threat an individual may pose to a target. Once an assessment is made, a plan can be developed and implemented to monitor the individual and to intervene, as appropriate, to prevent an attack. Attention to the individual's motives and attack-related behavior and to the systems (family, work, community, criminal justice, mental health, and social services) with which the individual is involved are the key to assessing and managing a potential threat. Once developed, a protective intelligence program will serve as a key component of a comprehensive protection program to prevent targeted violence.