This retrospective study of medical examiner records from three counties reported on 252 persons who killed 302 victims before killing themselves and reviews the Tarasoff ruling that set the standard for duty to warn and/or protect third parties whose lives are threatened by a patient. The three sites varied significantly for the perpetrator in terms of race, employment, cause of death, and motive. Female offenders killed more children under the age of 10 and adolescents than did male offenders. Evidence of premeditation included suicide notes and weapon brought to the crime scene, while strangulation indicated a spontaneous domestic homicide.