Authorities believe three AIM members shot and killed Annie Mae Aquash on the Pine Ridge reservation on the orders of someone in AIM's leadership because they suspected she was an FBI informant.
Two activists — Arlo Looking Cloud and John Graham — were both eventually convicted of murder. The third has never been charged.
Also in 1975, murder charges were filed against Means and Dick Marshall, an AIM member, in the shooting death of a Sioux man at a saloon in the town of Scenic, S.D. Marshall served 24 years in prison. Means was acquitted.
His activism extended to tribes beyond the United States. In the mid-1980s, Means traveled to Nicaragua to support indigenous Miskito Indians who were fighting the Sandinista government.
Born on the Pine Ridge Indian Reservation, Means grew up in the San Francisco area and battled drugs and alcohol as a young man before becoming an early leader of AIM.
With his rugged good looks and long, dark braids, he also was known for a handful of Hollywood roles, most notably in the 1992 movie "The Last of the Mohicans," in which he portrayed Chingachgook alongside Daniel Day-Lewis' Hawkeye.
He also appeared in the 1994 film "Natural Born Killers," voiced Chief Powhatan in the 1995 animated film "Pocahontas" and guest starred in 2004 on the HBO series "Curb Your Enthusiasm.
Means also ran unsuccessfully for the Libertarian nomination for president in 1988 and briefly served as a vice presidential candidate in 1984 on the ticket of Hustler publisher Larry Flynt.
Means always considered himself a Libertarian and couldn't believe that anyone would want to call themselves a Republican or a Democrat.
"It's just unconscionable that America has become so stupid," he said.
Means often refused interviews and verbally blasted journalists who showed up to cover his public appearances. Instead, he chose to speak to his fan base through YouTube videos and blog posts on his website.