The bombing the church where 4 girls were killed happened in 1963, the movie takes place in 1964-1965 why do you think the scene of the bombing was included in the film?

In Ava DuVernay's movie "Selma", four little Negro girls were included, they died violently in the 1963 16th Street Baptist Church Bombing in Birmingham, Ala. The movie "Selma" chronicles the Voting Rights Act campaign and communicates the terror of racist violence and is history as a horror movie.