People of color should not have to live in fear in the country that they too were born in. When Dylann Roof assaulted the people praying and doing bible study in the church in Charleston, he actually said that he was acting against them for racial reasons.
He is not a 'lone wolf' or a 'mentally ill person'. He is a product of the culture he grew up immersed in. A culture that glorifies White Supremacy and thrives on a inflated fear of The Other.
He wore the confederate flag and the Rhodesian flag as tributes to his 'ideal world'. A world where people of color are lesser, always. Are seen as little better then animals. There is little doubt that he was not in any way alone in these beliefs.
Charge him with the truth: Charge him with Domestic Terrorism and Hate crimes.