The Columbine High School massacre was a school shooting which occurred on April 20, 1999. Two senior students, Eric Harris and Dylan Klebold, murdered a total of 12 students and one teacher. They injured 21 additional students, with three other people being injured while attempting to escape the school. The pair then committed suicide. http://en.wikipedia.org/wiki/Columbine_High_School_massacre
In the ten years since the school massacre at Columbine High School in Colorado, school shootings have become an alarming epidemic. While sociologists have attributed the trigger of violence to peer pressure, such as bullying and social isolation, prominent psychologist Peter Langman argues here that psychological causes are responsible.