One of the deadliest school shootings in US history happened 12 years ago. When 2 seniors, Dylan Klebold and Eric Harris, killed 12 students and one teacher. The duo also injured 21 other students at Columbine High School in Littleton, CO.

Fox News Radio's Pam Pusso has the story:

Listen to a 911 call placed by teacher Patti Neilson, here:

Journals left behind by the gunmen show they had been planning the massacre for more than a year.

Listen here to file tape of then President Bill Clinton, reacting to the tragedy: