The Real-Life Horror Behind Leonardo DiCaprio's Latest Movie

The film, which will be coming to theaters in May, is based on a non-fiction book of the same name written by David Grann and released in 2017.

The book is set in the 1920s and follows the FBI as they probe a series of brutal slayings in Oklahoma.

However, what some may not know is that the book itself has roots in real life.

It's based on the true story of Ernest Burkhart, a man who lived in Oklahoma in 1921 and married into the Osage tribe with the encouragement of his dominating uncle.

Burkhart's marriage to Mollie Kyle, a full-blooded member of the Osage Nation, allowed him to join an exclusive group of white people who had gained access to the tribe's mineral rights, allowing them to make millions from oil drilling on Osage land.

During the roaring twenties, members of the Osage Tribe suddenly became rich when crude oil was found underneath their lands. As reported by the Oklahoma Historical Society, at its peak, yearly proceeds amounted to around $30 million.

Everything on the Osage Nation Reservation was owned and protected by the tribal government.

The royalties were divided equally among all of the tribe's members, with each recipient receiving a share referred to as a "headright." These headrights could only be obtained legitimately by outsiders if they tied the knot with a member of the tribe – something that William K. Hale from Greenville, Texas, knew he could take advantage of.

William had an unmarried nephew named Ernest Burkhart, who was quite reserved and submissive. To hatch his plan, he encouraged Ernest to marry an Osage member by the name of Mollie Kyle. The two got married in 1917, and Mollie switched her name to Mollie Burkhart.

Leonardo DiCaprio and Lily Gladstone star as Burkhart and Mollie, a couple living in Fairfax along with Mollie's mother, Lizzie Q. Meanwhile, William is played by Robert De Niro.

In May 1921, the decomposing body of Mollie's sister, Anna Brown, was found in a rugged gorge in Northern Oklahoma. Anna had a bullet wound in the back of her skull. It was certainly suspicious, but since she didn't appear to have any enemies, they were unable to track down the killer.

This tragedy left Lizzie shaken and heartbroken. Anna was the second of her 4 daughters to die within 3 years. Another daughter, Minnie, had "wasted away" and died in 1918.

Sadly, in July 1921, just two months after Anna died, Lizzie also died all of a sudden. She had no known illnesses prior to this, so the first thought everyone had was that she had been poisoned. However, no conclusive evidence of foul play ever came to light.

A year after that, Lizzie's nephew Henry Roan was subjected to the same tragedy in January 1923. Suspiciously, it was William who received his $25,000 life insurance policy.

Things calmed down for a while, but it didn't last long.

Tragedy struck the family yet again in March 1923 when Mollie's last surviving sister, Rita Smith, died due to a mysterious explosion at home. Her husband, William Smith, and their housekeeper, Nettie Brookshire, were also killed.

Following all of their deaths, Mollie, and therefore Ernest, inherited a fortune – to the tune of around $500,000 yearly.

The murders didn't stop there, however.

According to estimates, around 24 members of the Osage tribe died in a mysterious or violent way throughout the early 1920s. Newspapers described it as a 'reign of terror,' and it left many members of the tribe scared for their lives.

Finally, a panicked Osage Tribal Council decided to seek aid from the US government.

In 1923, the FBI got involved and started to investigate these mysterious murders. The case was arguably one of the bureau's earliest major investigations. It was also one of its first forays into organized crime investigation since getting established in 1908.

William quickly emerged as the primary suspect in the investigation. After all, the link between him and the first victim Anna Brown's family was pretty obvious to the authorities.

Once Anna, her mother, and her two other sisters died, the headright of the entire family would fall to Mollie. And Mollie, as mentioned earlier, was married to William's submissive nephew, who would do anything he said.

Additionally, William was known as 'King of the Osage Hills' around the area. It was no secret that he employed bribery and intimidation tactics as a means of attaining wealth and power. His eventual arrest alongside his accomplices, which included his nephew, Ernest, led to a sharp decrease in the number of killings by 1926.

After his involvement was officially confirmed, William underwent a trial and was sentenced to twenty years in prison. He was granted parole after serving two decades of the sentence in 1947.

An extensive investigation ensued, and it was revealed that the killers had already begun to poison Mollie – the last surviving member of her family.

Thankfully, the perpetrators were apprehended before she could be harmed any further. She recovered from the poisoning and separated from Ernest following the criminal proceedings, although they did already have kids at that point.

According to the film's actors, they all understand and recognize the weight of this film's real-life narrative. This is especially true for Janae Collins, a Native American actress who plays Mollie's sister, Rita.

"I'm so grateful to the Osage Nation for allowing us to tell their story. This is one of the most painful and heartbreaking time periods in the history of the Wazhazhe people as well as U.S. Native history," she says. "I take that very, very seriously as an actor and as a Lakota/Dakota and Apsáalooke woman."

Lily Gladstone feels the same way, "I consider it a true gift and great responsibility to be trusted with Mollie Burkhart, and will hold her preciously with both arms, close to my heart. My most profound thanks to Osage Nation, it is a remarkable gift to be welcomed by you, and to be able to tell this story. Iiksukapi, niksokowaiks."

Other cast members include Leonardo DiCaprio, Brendan Fraser, Jesse Plemons, and Robert De Niro. We can't wait to see Killers of the Flower Moon!