The exact date on which Martin Luther King, Jr. was killed was April 4, 1968. He was shot while standing on the balcony outside of his motel room in Memphis, Tennessee. He died on the same day. The shooter was a man named James Earl Ray.
King had come to Tennessee to help garbage workers who were striking for the right to form a union. This was in keeping with the fact that he had moved away from issues of civil rights and towards issues of economic justice. King had made this change after the Civil Rights Movement had won its battles over legal rights.