What Does ‘Active Shooter’ Really Mean? The New York Times(04)

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Columbine High School shooting 13 dead, dozens hurt in 1999 massacreColumbine 25 Years Later Impact Rachel's ChallengeColumbine High School shooting 13 dead, dozens hurt in 1999 massacreDeath Toll in 1999 Columbine School Shooting Climbs to 14 With HomicideWhat Does ‘Active Shooter’ Really Mean? The New York Times