Did some research and this is my best guess about the situation. The image was taken in front the Selma Courthouse in Alabama. Next door was Ted Gentry’s Chevrolet at 121 Lauderdale Street (as seen in the background of the photo).
From 1963-1965, there were a series of protests as part of the Voting Rights Movement.
One possible scenario for this picture could be: “On February 1 [1965], Martin [Luther King Jr] led a giant demonstration towards Selma courthouse. Martin and Ralph [Abernathy] along with 770 of the demonstrators were arrested… The white mechanics at Ted Gentry’s Chevrolet dealership came out to watch…” [P269 King: A Biography by David Lewis]
However, given the lack of other protestors in the background, it’s improbable this picture was shot in the presence of MLK, and I’m simply romanticizing the situation.
A more probable story would be: “The African-American group known as The Dallas County Voters League (DCVL) launched a voters registration campaign in Selma in 1963. Joined by organizers from the Student Nonviolent Coordinating Committee (SNCC), they began working that year in a renewed effort to register black voters.” [Wikipedia: Selma to Montgomery Marches] This would coincide with OP’s ‘1963’ date stamp.
As far as if this is actually Bernie Sanders, it’s possible. During that period, he was a member of the SNCC and was active against segregation. He has also been noted to have attended the March on Washington in 1963, so it wouldn’t be completely out of hand for him to have gone down to Alabama (all whilst being a student at University of Chicago). Here's a picture of him in 1963 http://www.politico.com/magazine/gallery/2015/07/bernie-sanders-the-early-years/002279-032662.html#.VrwyrPIrLDd