What Happened at Columbine?

On April 20, 1999, two students named Eric Harris and Dylan Klebold went on a shooting spree at Columbine High School, killing 12 students and 1 teacher before killing themselves. It was the worst school shooting in US history.
Deceased students: Rachel Scott, Corey Depooter, Kelly Fleming, Cassie Bernall, John Tomlin, Daniel Mauser, Kyle Velasquez, Lauren Townsend, Daniel Rohrbough, Steven Curnow, Matthew Kechter, Isaiah Shoels.
Deceased teacher: Coach William 'Dave' Sanders