As darkness fell on Canfield Drive on August 9, a makeshift memorial sprang up in the middle of the street where Michael Brown's body had been sprawled in plain view for more than four hours. Flowers and candles were scattered over the bloodstains on the pavement. Someone had affixed a stuffed animal to a streetlight pole a few yards away. Neighborhood residents and others were gathering, many of them upset and angry.

Soon, police vehicles reappeared, including from the St. Louis County Police Department, which had taken control of the investigation. Several officers emerged with dogs. What happened next, according to several sources, was emblematic of what has inflamed the city of Ferguson, Missouri, ever since the unarmed 18-year-old was gunned down: An officer on the street let the dog he was controlling urinate on the memorial site.

The incident was related to me separately by three state and local officials who worked with the community in the immediate aftermath of the shooting. One confirmed that he interviewed an eyewitness, a young woman, and pressed her on what exactly she saw. "She said that the officer just let the dog pee on it," that official told me. "She was very distraught about it." The identity of the officer who handled the dog and the agency he was with remain unclear.