You've been doing a lot of research on this.
Read the book by Laurence Hogan called The Osage Indian Murders. Hogan is retired from the FBI and a former Congressman.
AIM took the FBI file on the Osage and reworked the material into their propaganda and lies about Pine Ridge.
They even stole the same term, "Time of Terror" to describe the fabricated allegations of killing they made up at Pine Ridge.
The FBI files are on the Internet but are difficult to read and very long. Do a search for FBI+osage+indian
AIM takes this case and turns it on its head. They claim that the FBi protected killers/even killed Indians.
For good information on Pine Ridge go to http://www.noparolepeltier.com
This is very complicated because the people are so crazy that it doesn't seem to make sense.