Background: Following the April 20, 1999, massacre at Columbine High School, Littleton, Colo, school administrators, law enforcement officials, and the media reported a rash of successive bomb threats and threats of school violence that were attributed to imitation.
Objective: To establish that the clustering of threats of school violence following the Columbine massacre was initiated by imitation.
Design: A database of threats of school violence reported to the Pennsylvania Emergency Management Agency, Harrisburg, during the 50 days following the Columbine incident was examined to determine the daily frequency of threats. To determine factors that predict the occurrence of these threats, counties and school districts in which threats occurred were noted.
Results: Pennsylvania school districts reported 354 threats of school violence during the 50 days after the Columbine massacre, far exceeding the 1 or 2 threats per year estimated by school administrators before 1999. The frequency of these threats over time demonstrated a crescendo-decrescendo pattern. Fifty-six percent of the threats were made on or before day 10 after the incident, and more than one third occurred on days 8, 9, and 10. Factors that predicted the likelihood of a school's receiving a threat after the massacre included a greater proportion of white students and larger school enrollment.
Conclusions: Successive threats of violence follow a publicized act of school violence. The media should recognize that imitation threats can occur and craft their stories accordingly.