Nearly four years ago, a Chicago police officer shot a teenager 16 times from 10 feet away. The teen had been behaving erratically while walking down the street, and at the time of the shooting was holding a folding knife with a three-inch blade. He did not obey police commands to drop the weapon, and then was shot.

The Chicago Police initially ruled the shooting justified. However, dashcam footage released 13 months later revealed that the teen was walking [...]