Eric David Harris and Dylan Bennet Klebold were American high school seniors who perpetrated the Columbine High School massacre at Columbine High School on April 20, 1999 in Columbine, Colorado. Harris and Klebold killed 12 students, one teacher, and wounded 24 others. After killing most of their victims in the school's library, they died by self-inflicted gunshot wounds. At the time, it was the deadliest high school shooting in U.S. history.

School bullying, like bullying outside the school context, refers to one or more perpetrators who have greater physical strength or more social power than their victim and who repeatedly act aggressively toward their victim. Bullying can be verbal or physical. Bullying, with its ongoing character, is distinct from one-off types of peer conflict. Different types of school bullying include ongoing physical, emotional, and/or verbal aggression. Cyberbullying and sexual bullying are also types of bullying. Bullying even exists in higher education. There are warning signs that suggest that a child is being bullied, a child is acting as a bully, or a child has witnessed bullying at school.