title: The psychological reactions after witnessing a killing in public in a Danish high school.
abstract: BACKGROUND
  School killings attract immense media and public attention but psychological studies surrounding these events are rare.
  
  
  OBJECTIVE
  To examine the prevalence of posttraumatic stress disorder (PTSD) and possible risk factors of PTSD in 320 Danish high school students (mean age 18 years) 7 months after witnessing a young man killing his former girlfriend in front of a large audience.
  
  
  METHODS
  The students answered the Harvard Trauma Questionnaire (HTQ), the Crisis Support Scale (CSS), and the Trauma Symptom Checklist (TSC).
  
  
  RESULTS
  Prevalence of PTSD 7 months after the incident was 9.5%. Furthermore, 25% had PTSD at a subclinical level. Intimacy with the deceased girl; feeling fear, helplessness, or horror during the killing; lack of expressive ability; feeling let down by others; negative affectivity; and dissociation predicted 78% of the variance of the HTQ total scores.
  
  
  CONCLUSIONS
  It is possible to identify students who are most likely to suffer from PTSD. This knowledge could be used to intervene early on to reduce adversities.
authors: National Centre for Psychotraumatology, University of Southern Denmark, Odense, Denmark.
authors: Ask
authors: A
authors: Elklit
authors: Sessel
authors: S
authors: Kurdahl
keywords: PTSD; risk factors; social support; witnessing school killing