Today marks the 20th anniversary of the attack on Columbine High School: On April 20, 1999, 2 teenage boys dressed in black trench coats killed 12 classmates and a teacher, and wounded 2 dozen others before taking their own lives.
Why it matters: Now, the survivors are raising kids in a world shaped by the attack. "Drills teaching students to 'lock down' inside classrooms became routine. Schools formed teams to assess threats, particularly from students. And security firms forged a multibillion-dollar industry, introducing surveillance video, panic buttons and upgraded doors and locks," AP reports. And, sadly, mass shootings have become part of growing up in America.