It has been nearly 20 years since the first mass school shooting in the U.S. -- the shocking tragedy at Columbine High School in Littleton, Colorado, on April 20, 1999. As a “credible” threat ...

It's so comforting to see kids walking back into the building for the first time since the 20th,'' he said. While most students entered the high school cheering and smiling, the Columbine rally's ...

"It's my understanding that at one time, we had SWAT teams in the building that were unaware of each other ... a child's fantasyland of miniature houses and trains about 15 miles west of Columbine ...

Sitting in the library at Columbine High School, his son's shoes on his feet ... and then there were some buildings next door that were still under construction, 'Oh, what's that?' ...