School shooters are narcissistic, heavily involved in video game play and/or the consumption of other violent media contents, neglected by parents, and introverts rejected if not bullied by peers. Or are they?
This stereotypic picture of a school shooter has often been drawn in the media and has strongly influenced the public imagination of a typical offender. But research on school shootings that was not based on the analysis of media reports shows a much more complex picture. Both North American and European school shooters displayed a broad range of different and sometimes contradicting characteristics, problems, and behavior patterns: For example, although some offenders reportedly were the victims of bullying, seemingly most were not. Instead, although not necessarily being well liked by all peers, most had a close circle of friends. There have been school shooters without any mental health problems and those who were sometimes narcissistic, but more often showed other problems, such as (unmasked) low self-esteem, depressive traits, other personality disorders, and the like. Finally, many school shooters displayed a strong interest in violent video games, but also in books, films, or music. And in some cases, there was no indication of such an interest at all [1, 2]. Consequently, one of the most consistent findings on school shooters is that there is no consistent profile of school shooters.
Can We Prevent School Shootings?
If a typical offender profile does not exist, is it possible to prevent school shootings at all? Indeed, there seems to be a way, because research has yielded a second consistent finding: School shootings are no spontaneous acts and in all known cases, the later perpetrators (publicly) announced their offenses prior to carrying it out. These announcements have been termed “leaking” . In some cases, leaking was verbal and very detailed (e.g., when the later offenders talked about wanting to kill a specific teacher at a specific date). In other cases, leaking was rather vague and mostly expressed through concerning behaviors and/or changes in behavior prior to the offenses (e.g., showing an interest in similar offenses, giving away personal goods). In all cases, however, leaking tended to occur repeatedly, over extended periods of time (i.e., several days to several years), in different ways, and in front of a large number of witnesses. There are two further characteristics that make leaking important for preventive efforts: First, leaking seems less frequent than most potential risk factors or even their combinations. For example, a much smaller number of persons show leaking than become victims of bullying. Second, there seem to be ways to adequately assess the seriousness of even rather vague leaking behaviors. One last important finding is that different groups of offenders showed clearly different patterns of leaking behavior .
Taken together, the proper identification and assessment of leaking are particularly important starting points for the prevention of school shootings. Therefore, and because leaking mostly occurred in the peer context, it seems pivotal to prepare not only the police, but also schools for these tasks . Indeed, previous research showed that a number of planned school shootings were prevented due to information by other students  and sometimes even by parents (see report of a recent school shooting thwarted in Salt Lake City, Utah). Hence, in order to find a rational approach to the prevention of school shootings, it is apparently reasonable to put a primary focus on warning signs for a potential offense, such as leaking. Potential additional risk factors should then be considered and assessed in a secondary appraisal in order to determine whether a person may be on the way to commit such an offense.
Rebecca Bondü is a visiting professor for developmental psychology at the Department of Psychology at the University of Konstanz in Germany.
 Vossekuil, B., Fein, R.A., Reddy, M., Borum, R. & Modzeleski, W. (2002). The final report and findings of the Safe School Initiative: Implications for the prevention of school attacks in the United States. Washington: U.S. Secret Service and U.S. Department of Education.
 Bondü, R. & Scheithauer, H. (2015). Kill one or kill them all? Differences between single and multiple victim school attacks. European Journal of Criminology, 12, 277-299. doi: 10.1177/1477370814525904.
 O’Toole, M.E. (1999). The school shooter: A threat assessment perspective. Federal Bureau of Investigation.
 Leuschner, V., Bondü, R., Schroer-Hippel, M., Panno, J., Neumetzler, K., Fisch, S., Scholl, J. & Scheithauer, H. (2011). Prevention of homicidal student violence in Germany: The Berlin Leaking Project and the Networks Against School Shootings Project (NETWASS). New Directions for Youth Development, 129, 61-78, doi:10.1002/yd.387.
 Daniels, J.A., Volungis, A., Pshenishny, E., Gandhi, P., Winkler, A., Cramer, D.P. & Bradley, M.C. (2010). A qualitative investigation of averted school shooting rampages. The Counseling Psychologist, 38, 69-95. doi: 10.1177/0011000009344774