The official version of events begins with an April 30th 1866 confrontation between police & a group Black former soldiers that had been out drinking. The group of officers attempted to force the men off of the sidewalk, and when one of the officers fell to the ground, guns were drawn & a fight ensued. The next day (May 1st) a larger group of Black Men, mostly former soldiers, were assembled for yet another standoff. Officers arrived, a scuffle ensued, and all hell broke loose as the officers began firing upon the crowd of retreating Black citizens. At the urging of City Recorder John C. Creighton, a mob was assembled with instructions to "kill every Negro and drive the last one from the city." The mob of Policemen, Firemen & more, would go on to loot and burn every home in the area. On May 2nd, a second wave of violence hit with little regard for women or children (official reports state that some were even shot while still in bed).
"All crimes imaginable were committed from simple larceny to rape and murder. Several women and children were shot in bed. One woman (Rachel Johnson) was shot and then thrown into the flames of a burning house and consumed. Another was forced twice through the flames and finally escaped. In some instances houses were fired and armed men guarded them to prevent the escape of those inside."
There are no clearly defined reasons as to what caused the rampage to finally cease, but as of May 4th, it was finally over. In the end, it is estimated that 90-100 homes, 12 schools, & four churches were laid to waste. At least five women were raped, and 285 people were injured. None of the perpetrators were ever arrested for their crimes.
http://www.blackpast.org/aah/memphis-riot-1866
http://teachingamericanhistory.org/library/document/the-freedmens-bureau-report-on-the-memphis-race-riots-of-1866/