Video: 'Hammarskjold's Death Shocks The World (1961)'

(Monday, September 18, 1961, 12:13 a.m. Central Africa Time; during the 1961 Ndola United Nations DC-6 crash) — United Nations Secretary-General Dag Hammarskjold, 56, was killed today when his plane crashed under mysterious circumstances nine miles west of Ndola in Northern Rhodesia (now Zambia) while en route to cease-fire negotiations during the Congo Crisis, part of the Decolonisation of Africa and the Cold War.

Video: 'Unexplained Crash of Flight DC-6 | Air Crash Investigation | National Geographic UK'

The circumstances of the crash are still unclear. A 1962 Rhodesian inquiry concluded that pilot error was to blame, while a later UN investigation could not determine the cause of the crash. There is evidence suggesting the plane was shot down. A CIA report implicated the KGB, the main security agency for the Soviet Union.

The day after the crash, former U.S. President Harry Truman commented that Hammarskjöld “was on the point of getting something done when they killed him. Notice that I said ‘when they killed him.'”