Did you get to see the movie "Selma"? It is worth watching - a fine film. Although it is certainly not a documentary, it seems to me more an impression of those fateful days in the Civil Rights Movement - still an important story that is rarely told in this way.
So to add to that, here is a moving, insightful short documentary (A Call from Selma) featuring UU minister Rev. Clark Olsen that fills in the story of the murder of Rev. James Reeb, and reminds us of this uncomfortable fact: As Dr. Martin Luther King Jr. notes in 1967, “The failure to mention Jimmy [sic] Jackson only reinforced the impression that to white Americans the life of a Negro is insignificant and meaningless.” Fifty years after Bloody Sunday, these issues are as important as ever.