On this day, Aug. 29, in 1970, police Sgt. Frank Von Colln was killed by radicals in Philadelphia. Von Colln, 43, a father of four, was talking on the phone in a stone guardhouse when he was shot five times in the back. Prosecutors said the killers belonged to a group called the Black Unity Council, and planned to kill police and bomb station houses.

The shooting of Von Colln and another officer marked the beginning of three days of violence in the city that left six officers wounded.