 Complete the following phrase:  The Emmett Till trial in September 1955 was the early catalyst for the civil rights movement. McMahons on-site and on-deadline images from Mississippi, published nationwide in Life magazine, provided the visualization that helped spur Rosa Parks refusal to give up her seat on the bus in December 1955, which then led to the Montgomery bus boycott and to bringing Martin Luther King Jr. to national attention, along with fellow boycott leader Ralph Abernathy. McMahon was in attendance for Kings I Have a Dream speech during the August 1963 