An unidentified woman stands among 15 crosses posted on a hill above Columbine High School in Littleton, Colo., on April 28, 1999. As the Los Angeles Times reported, two seniors -- Eric Harris and Dylan Klebold -- killed 12 students and one teacher. They also injured 21 other students; three people were injured while attempting to escape. The pair later committed suicide. The Columbine shootings were the fourth-deadliest school massacre in United States history.
Eric Gay / Associated Press
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