In the video, Flint Farmer was lying on the grass between the curb and the sidewalk. It was shortly before 2 a.m. on a June morning in the West Englewood neighborhood, and Farmer had been shot by a Chicago police officer. Then, according to the video, the veteran officer, Gildardo Sierra, stepped onto the parkway and walked a semicircle about the prone Farmer as three bright flashes went off.