Colorado school shooter may have had grudge against teacher

A teenager who may have had a grudge against a teacher opened fire with a shotgun at a US high school, wounding two students before killing himself.

Quick-thinking students at Arapahoe High School in Denver, Colorado, alerted the targeted teacher, who quickly left the building. The scene unfolded on the eve of the Newtown massacre anniversary, a sombre reminder of the ever-present potential for violence in the nation’s schools.