From the archives: School shooters

On the 60 Minutes broadcast this week, Scott Pelley reported on the incomprehensible school massacre in Newtown, Connecticut -- and what could have possibly driven 20-year-old Adam Lanza to murder innocent children at Sandy Hook Elementary School.

Trying to understand the mind of a school shooter is a story Pelley has been reporting for over a decade. In the above video, you'll see where the story began for Pelley and his then-producer Bill Owens, who is now executive editor of the 60 Minutes broadcast.

Their two-part report, titled "Mind of the Assassin," aired on 60 Minutes II in March of 2000. In part one, Pelley and Owens first reported on a U.S. Secret Service research study aimed at stopping assassins and school shooters before they strike. Part two discussed the Secret Service's National Threat Assessment Center and its efforts to prevent school shootings.

Note from the editor: After this story aired, 60 Minutes published the following correction:

"We heard from the developer of Mosaic-2000, a computer program that attempts to assess the risk that a student could turn violent. He says that, 'Since Mosaic analyzes specific threats, we were wrong to imply that the Secret Service thinks Mosaic is a form of profiling and a waste of time.' He's right. The Secret Service never said that and it does not critique any such program one way or the other."