The horrific true story behind Leonardo DiCaprio’s new movie

Leonardo DiCaprio’s new film Killers of the Flower Moon explores the gripping true story of the “reign of terror” that left two dozen Native Americans dead.

The blockbuster, due out in May, is based on the 2017 non-fiction book of the same name, written by David Grann.

It takes place in the 1920s revolves around the FBI’s investigation into a series of murders after several members of the Oklahoma Osage tribe were slaughtered.

But as movie fans gear up for the crime drama to reach their screens, FEMAIL takes a look back at the gruesome true story.

New film Killers of the Flower Moon explores the gripping true story of the ‘reign of terror’ that left two dozen Indians dead. Pictured: Lily Gladstone as Mollie Kyle and Leonardo DiCaprio as Ernest Burkhart

Born in Greenville, Texas, William K. Hale encouraged his subservient cousin Ernest Burkhart to marry Osage member Mollie Kyle (pictured)

Born in Greenville, Texas, William K. Hale encouraged his subservient cousin Ernest Burkhart (pictured) to marry Osage member Mollie Kyle

Born in Greenville, Texas, William K. Hale encouraged his subservient cousin Ernest Burkhart (right) to marry Osage member Mollie Kyle (left)

Killers of the Flower Moon focuses on a little-publicized chapter of American history involving the Osage Nation.

In the 1920s, the Osage tribe became wealthy almost overnight after oil was discovered under their land, bringing them more than $30 million in annual income at the peak of the boom, according to the Oklahoma Historical Association.

Underground minerals within the Osage Nation reservation were tribal property and held in trust by the government.

Mineral leases provided royalties that were paid to the tribe as a whole – with each entitled party receiving an equal share, known as a headright.

But these headrights could only be obtained legally by outsiders if they married into the tribe.

It was at this time that farmer William K. Hale, a resident of Greenville, Texas, encouraged his submissive cousin Ernest Burkhart to marry Osage member Mollie Kyle (later Mollie Burkhart).

Burkhart, played by Leonardo DiCaprio, and wife Mollie, played by Lily Gladstone, lived in Fairfax with Mollie’s mother Lizzie Q.

Lizzie was a mother of four, and in May 1921, the decomposed body of one of the other daughters, Anna Brown, was discovered in a remote canyon in northern Oklahoma.

In May 1921, Osage-born Anna Brown was found with a bullet hole in the back of her head - but her case remained unsolved

In May 1921, Osage-born Anna Brown was found with a bullet hole in the back of her head – but her case remained unsolved

Her decomposed body was found in a remote ravine (pictured) in the Osage Hills of northern Oklahoma

Her decomposed body was found in a remote ravine (pictured) in the Osage Hills of northern Oklahoma

She was found with a bullet hole in the back of her head, but because Brown had no known enemies, the case remained unsolved.

Just two months later, Lizzie herself died of suspected poisoning under suspicious circumstances, though no evidence has ever been found.

Then another member of the family, Lizzie’s cousin Henry Roan, met a similar fate in January 1923 with Hale, played by Robert De Niro, who fraudulently named himself as the beneficiary of his $25,000 life insurance policy.

But the deaths within the family didn’t stop there.

In March 1923, another of Lizzie’s daughters, Rita Smith, along with Rita’s husband William Smith, and their housekeeper Nettie Brookshire were all killed when their home was destroyed by an explosion.

And after their deaths, Burkhart and Mollie inherited a fortune from her mother’s and sisters’ estates.

But the killings extended beyond one family, with estimates that 24 Osage Indians died in violent or suspicious deaths throughout the early 1920s, with newspapers at the time labeling it a “reign of terror.”

William Hale, played by Robert De Niro, was accused of bribing and intimidating others to do much of his dirty work on his way to acquiring money and power

William Hale, played by Robert De Niro, was accused of bribing and intimidating others to do much of his dirty work on his way to acquiring money and power

Members of Lizzie Q's family (pictured) were called in quick succession, including her cousin Henry Roan

Members of Lizzie Q's family were called in quick succession, including her cousin Henry Roan (pictured)

Members of Lizzie Q’s family (left) were called in quick succession, including her cousin Henry Roan (right)

By this time, authorities were growing suspicious and an alarmed Osage Tribal Council sought the help of the US government.

Hale’s name came up early in the investigation as the mastermind behind the murders.

The so-called ‘King of the Osage Hills’ was accused of bribing and intimidating others to do much of his dirty work while seeking money and power.

The killings stopped after Hale, along with accomplices, including his cousin, were arrested in 1926.

Hale was formally convicted of his involvement three years later. He was paroled in 1947 after serving two decades of his sentence.

At the time, investigators also found that the killers had already begun poisoning Mollie in what would have been the final piece of the crook’s master plan.

Happyshe recovered and divorced her murderous husband after the trial.

In the 1920s, the Osage Tribe (pictured with President Coolidge) became wealthy almost overnight after oil was discovered under their land

In the 1920s, the Osage Tribe (pictured with President Coolidge) became wealthy almost overnight after oil was discovered under their land

Underground minerals within the Osage Nation reservation were tribal property and held in trust by the government

Underground minerals within the Osage Nation reservation were tribal property and held in trust by the government

Actors involved in the production recognized the seriousness of the film’s true story.

Lily Gladstone previously shared a photo of Mollie Burkhart on Instagram, along with a caption that read, “I consider it a true gift and a great responsibility to be trusted with Mollie Burkhart, and will hold her precious with both arms, close to my heart.

“My deepest thanks to Osage Nation, it is a remarkable gift to be welcomed by you and to be able to tell this story.”

Janae Collins, who plays Rita Smith, also wrote, “I am so grateful to the Osage Nation for letting us tell their story. This is one of the most painful and heartbreaking periods in the history of the Wazhazhe people, as well as American Native history and

“I take that very, very seriously as an actor and as a Lakota/Dakota and Apsáalooke woman. I am very grateful to Marty Scorsese for the truthfulness, dedication and care he put into this project. He and Leonardo really battled for us (as Natives) over the years to get to the point where we’re ready to film.

“I am so grateful/grateful for the love and support we have received.”