Bells tolled 39 times across the United States on Wednesday to mark Martin Luther King Junior's assassination outside a Memphis motel 50 years ago. The number represents the amount of years the American civil rights campaigner lived. At the age of 39, King had become the leader of a non-violent initiative for equal rights for African-Americans. His death rocked the US in a year that would also bring race riots, anti-war demonstrations and the assassination of presidential candidate, Robert Kennedy.