Columbine families and the latest US gun tragedy

In 1999, in one of the most infamous gun tragedies in US history, two teenage boys stormed their school, spraying bullets and killing 13 people before turning their weapons on themselves. It was seen as a watershed moment — but now, just 20 miles down the road, another gunman's bloodbath has convinced some Columbine families the nation has learned nothing from their sad history. Duration: 02:07