The Trench coat Mafia Opinion MANY FACTORS CAUSED OUTBURST OF VIOLENCE There is no single factor that caused the outburst of violence on 20th April 1999, in Littleton, Colorado. Blaming a single factor as the cause of the Columbine High School massacre is as ludicrous as a nation blaming an economic crisis on one person alone. There were many contributing factors that led to this massacre, and with that, an array of warning signs, all of which were ignor ....