Leonardo DiCaprio and Martin ScorseseMartin Scorsese and Leonardo DiCaprio are teaming up for their sixth film, which is based on the 1920s true-crime thriller "Killers of the Flower Moon: The Osage Murders and the Birth of the FBI."

Variety reports that Scorsese will start work on the film after the gangster movie "The Irishman," which stars his other favorite leading man, Robert De Niro.

"Killers of the Flower Moon" is about a series of murders of members of the Osage tribe in Oklahoma after oil was discovered on their land. The slayings became one of the FBI's first major homicide investigations. It's based on the bestselling book by David Grann, who also wrote the adventure story "The Lost City of Z."

The rights reportedly sold for $5 million and Oscar-winning writer Eric Roth of "Forrest Gump" and "The Curious Case of Benjamin Button" fame is said to be working on the script.

Dante Ferretti, Scorsese's longtime production designer, told Variety that Scorsese hoped to start shooting "Flower Moon" next spring. Ferretti says he will be scouting locations in Oklahoma. "The whole 1920s world of the Indians who lived there needs to be reconstructed," Ferretti told Variety.

Scorsese is gearing up to start shooting "The Irishman," about mob hit-man Frank Sheeran, this September.

He and DiCaprio earlier announced plans to film another true crime story, "The Devil in the White City," in which DiCaprio would play infamous 19th century serial killer H.H. Holmes.