At the time, the Osage (a Native American community in the States) was considered one of the richest communities in the world, white or otherwise, due to being on a large inland oil deposit. By all accounts, some of the Osage got very rich, but it also opened the door for greed and corruption from outside. The government passed a law that anyone of half blood or more needed to have a legal guardian until they were proved mentally fit--that guardian being drawn from the white community outside. Moreso, it saw white men entering the community to marry Osage women, with the aim of then murdering the new wife to take control of the land that she owned. There is a book by Dennis McAuliffe, Bloodland, that explores the time and reportedly ends in the realisation that his grandfather murdered his grandmother, for just that. The deaths weren't just related to women, either, as men were murdered as well. According to a New York Times article out of the late nineties, by 1925, over 60 men and women had been murdered for their land and the wealth they had inherited.
The FBI, under Hoover, were eventually called in and saw a handful of men arrested, including a man by the name of Bill Hale, who called himself the King of the Osage Hills, though the majority of the murders, long buried by corruption, were never bought to justice. Though if such a thing would have been done at the hands of the FBI remains another question.
I thought it a terrible and fascinating story, one that I am sure is not unique or, sadly, dated in its example of human greed. By all accounts there's a bunch of books written about it, including John Joseph Mathews' Sundown, who was a member of the Osage Tribal Council later.