I was one of the first reporters on scene at the Columbine shootings on April 20, 1999. And I covered it continuously, as a local newspaper reporter and eventually as a book author, for 10 years.

The 2002 Safe School Initiative report, by the Secret Service and the Department of Education, looked at 41 attackers across 37 incidents from 1974 to 2000. It concluded that only 17 percent "had been ...