killer of the flower moon By brennanfender 1920 Osage Nation members in Oklahoma become wealthy from oil revenues. Osage Nation members in Oklahoma become wealthy from oil revenues. Period: 1921 to 1925 A series of suspicious deaths occur among the Osage people 1923 The newly formed FBI, led by J. Edgar Hoover, assigns agent Tom White to investigate the Osage murders. 1926 Authorities arrest William Hale, Ernest Burkhart, and their accomplices.