Coniston massacre
The Coniston massacre, which took place near the Coniston cattle station in the then Territory of Central Australia (now the Northern Territory) from 14 August to 18 October 1928, was the last known officially sanctioned massacre of Indigenous Australians and one of the last events of the Australian Frontier Wars. People of the Warlpiri, Anmatyerre, and Kaytetye groups were killed. The massacre occurred in revenge for the death of dingo hunter Frederick Brooks, killed by Aboriginal people in August 1928 at a place now known as "Yukurru", also known as Brooks Soak.
CIA Kennedy assassination conspiracy theory
John F. Kennedy, the 35th President of the United States, was assassinated in Dallas, Texas, on November 22, 1963. Various agencies and government panels have investigated the assassination at length, drawing different conclusions. Lee Harvey Oswald is accepted by official investigations as the assassin, but he was murdered by Jack Ruby before he could be tried in a court of law. The discrepancies between the official investigations and the extraordinary nature of the assassination have led to a variety of theories about how and why Kennedy was assassinated. 
The House Select Committee on Assassinations (HSCA) concluded in 1979 that Oswald assassinated Kennedy, but that a conspiracy was probable. The committee did not implicate U.S. Intelligence agencies. Their conclusion was reached almost entirely because of the results of forensic analysis of a police dictabelt, which supposedly recorded the sound of a fourth bullet being fired in Dealey Plaza.