The Columbine High School massacre Killing was a school shooting Use_firearm and attempted bombing Attack that occurred Coming_to_be on April 20 , 1999 , at Columbine High School in Columbine , Colorado , United States .

The Columbine High School massacre Killing was a school shooting Use_firearm and attempted bombing Attack that occurred Coming_to_be on April 20 , 1999 , at Columbine High School in Columbine , Colorado , United States .

The Columbine High School massacre Killing was a school shooting Use_firearm and attempted bombing Attack that occurred Coming_to_be on April 20 , 1999 , at Columbine High School in Columbine , Colorado , United States .

The crime Violence has inspired Influence several copycats , had an impact Influence on pop culture ( see Columbine effect ) and `` Columbine '' has become Becoming a byword for mass shootings Use_firearm .

The crime Violence has inspired Influence several copycats , had an impact Influence on pop culture ( see Columbine effect ) and `` Columbine '' has become Becoming a byword for mass shootings Use_firearm .

Columbine also resulted in Causation an increased Cause_change_of_position_on_a_scale emphasis on school security with zero tolerance policies .

The Columbine Memorial opened Openness up to the public on September 21 , 2007 .