As someone who is black and impacted by these recent events - think of them as a giant pouring of gasoline on an already present fire. People are grieving pain that has been present for years. People grieve in different ways. I don't agree with using violence, looting, rioting as a means of grieving, yet I can fully understand why others have taken that route. The riots are in fact a symptom...not an excuse. It's a fact. Slavery was a "well known problem", but it took the Civil War to see the Emancipation Proclamation come into fruition.
Getting rid of racism in America's systems and in individuals is going to take a lot of effort along with moments like this where everyone is reminded of exactly how much progress is left.