Nathan Chasing Horse trained his wives to use firearms – telling them to “shoot it out” with police officers if they ever tried to “break their family apart”, according to records.
If that failed, the Dancing With Wolves actor said they should take “suicide pills”, the papers, obtained by the Associated Press (AP), said.
The alleged abuse, which authorities say spanned two decades, led to the arrest of Chasing Horse on Tuesday after a months-long investigation by Las Vegas police.
He was held as he left the home he shares with his five wives in north Las Vegas.
Swat officers were seen outside the two-storey home as detectives searched inside.
During the raid, police allegedly found memory cards containing videos of sexual assaults, firearms and 41lb (18.6kg) of marijuana and psilocybin mushrooms, an arrest report released on Wednesday said.
Known for his role as the young Sioux tribe member Smiles A Lot in the Oscar-winning Kevin Costner film Dances With Wolves (1990), Chasing Horse gained a reputation among tribes across the United States and in Canada as a so-called medicine man who performed healing ceremonies.
But police said he abused his position, physically and sexually assaulting Indigenous girls and women, taking underage wives and leading a cult.
Chasing Horse, 46, will be charged with at least two counts of sex trafficking and one each of sexual assault of a child under 16, child abuse or neglect and sexual assault, according to court records.
Authorities have not said when he will be formally charged.
He is in jail awaiting his first court appearance, which is expected on Thursday.
Chasing Horse is believed to be the leader of a cult known as The Circle, according to a 50-page search warrant seen by the AP.
At least two women told police Chasing Horse showed his wives a stash of “small white pills”, which he called “suicide pills”, at some point in 2019 or 2020.
The women were instructed to “take a pill to kill themselves in the event he dies or law enforcement tries to break their family apart”, the warrant said.
One of Chasing Horse’s former wives also told police she believed his current wives would “carry out the instructions” to take the pills and open fire if police went to arrest him.
Las Vegas police said in the document they have identified at least six sexual assault victims, some as young as 14 when they say they were abused, and traced the sexual allegations against Chasing Horse to the early 2000s in multiple states, including Nevada, where he has lived for about a decade, South Dakota and Montana.
“Nathan Chasing Horse used spiritual traditions and their belief system as a tool to sexually assault young girls on numerous occasions,” detectives wrote in the warrant, saying his followers referred to him as Medicine Man or Holy Person because they believed he could communicate with higher beings.
One of Chasing Horse’s wives was offered to him as a “gift” when she was 15, according to police, while another became a wife after turning 16.
Chasing Horse is also accused of recording sexual assaults and arranging sex with the victims for other men who paid him.
He was arrested nearly a decade after he was banished from the Fort Peck Reservation in Poplar, Montana, amid allegations of human trafficking.
Fort Peck tribal leaders voted 7-0 to ban Chasing Horse from stepping foot on the reservation again, citing the trafficking allegations in addition to accusations of drug dealing, spiritual abuse and intimidation of tribal members, Indian County Today reported.
State attorneys general and politician around the US are looking into creating specialised units to handle cases involving Native American women.
In South Dakota, where police said Chasing Horse committed some of his crimes, the attorney general’s office has put a new focus on crimes against Native American people, including human trafficking and killings.
Chasing Horse was born on the Rosebud Reservation in South Dakota, which is home to the Sicangu Sioux, one of the seven tribes of the Lakota nation.