How is violence ineffective during civil rights?

In 1955, Reverend George Lee, vice president of the Regional Council of Negro Leadership and NAACP worker, was shot in the face and killed for urging blacks in the Mississippi Delta to vote. Although eyewitnesses saw a carload of whites drive by and shoot into Lee's automobile, the authorities failed to charge anyone. Governor Hugh White refused requests to send investigators to Belzoni, Mississippi, where the murder occurred.