What do you think was the real motivating factor that caused the massacre as depicted in the documentary Dreamland: The Burning of Black Wall Street?

On CNN tonight I watched this devastating documentary of a 1921 massacre of innocent people by an angry racist mob. I also learned that while people were running for their lives, that shots were being fired by planes over head. That in the end 16 hours later much of what it was built was completely demolished and the residents were forced off the properties that they legally owned! i think that it was more than racism involved.