SINGAPORE – Director Martin Scorsese is known for violent crime thrillers.

But he also makes cultural films that portray life in a non-white community, which have nothing to do with the Italian- or Irish-American criminal underworld viewers have become so familiar with.

In Killers Of The Flower Moon – what critics are calling his best in recent times – he combines the violent crime thriller with the cultural study of a people whose values were at odds with the larger community.

Scorsese bristles slightly when asked why he thought it was necessary to show the executions of Native Americans by gunshot and explosives.

“You know, the violence isn’t going to go away if you don’t see it,” says the 80-year-old giant of American film-making, who was answering a question from The Straits Times during an online press conference.

“You can sweep it under the rug and say it never happened. But it won’t go away. You have to know what humans are capable of doing.”

In Scorsese’s acclaimed mob movies like Goodfellas (1990), Casino (1995) or The Departed (2006), the ruthlessness of gangsters is left in no doubt. Bodies pile up.

Bearing witness to the historical injustice of the Osage murders is crucial today, he says.

Opening in Singapore cinemas on Thursday, Killers Of The Flower Moon depicts events that took place from around World War I to the 1930s, when the indigenous people of Osage County, Oklahoma, were murdered for their oil rights money by white interlopers who claimed to be there to serve and protect them.

“We have to see what they did,” Scorsese reiterates, adding that violence on screen has a cathartic purpose – it releases pent-up feelings.

“Violence is part of human nature and to deny that, to push it away, makes it worse.”

The principle of never flinching from depicting the cruel side of human nature has followed him over a career that began in the late 1960s – and has made the questions about his use of violence a regular occurrence.

“I’ve had this question since 1972,” he says.

Scorsese also spoke about why, in adapting the 2017 book Killers Of The Flower Moon: The Osage Murders And The Birth Of The FBI by American journalist David Grann, he had a change of heart about the direction the story was going.

The source material and the early screenplays that sprung from it mostly followed the Federal Bureau of Investigation agents sent to investigate the deaths.

“I would be making a film which would have been – and I do not mean this in a derogatory way – a police procedural. I enjoy watching them, but I don’t know if I wanted to make it that way,” he says.

After speaking to members of the Osage native community in Oklahoma and understanding their culture, he realised that he wanted to “deal with them on a solid level, in an authentic way and also with more compassion”.

And upon discussing with lead actor Leonardo DiCaprio, Scorsese came to the conclusion that the relationship between DiCaprio’s Ernest, a WWI veteran, and Mollie, an Osage woman played by Lily Gladstone, would unlock the film.

Scorsese says: “The heart of the film is the love story.”

And so, despite having worked on it for several years, the film-maker scrapped the screenplay in favour of a rewrite that placed the police investigation in the background.

He also addressed criticism of the epic western crime saga’s 3½-hour running time.

“Come on. You could sit in front of a TV and watch something for five hours. I’ve done it. And many people go to the theatre to see a play that runs 3½ hours. You have to give the cinema some respect,” he says.

Geoffrey Standing Bear, principal chief of the Osage Nation, said in a separate interview that he gave the production his support after being certain Scorsese’s team was not going to take the usual Hollywood shortcuts.

The 70-year-old leader says: “We did not want to be stereotyped. We wanted to hear our language, not another tribal language.”

And instead of filming Killers Of The Flower Moon in a state that would give financiers generous tax breaks, Scorsese assured him that the movie would be shot in Oklahoma and the story would be seen through the eyes of Mollie.

Chief Standing Bear says: “We were sceptical, of course. But he proved it to us. He and Leonardo DiCaprio met our community and our elders. Leo was with him at many of these meetings and they became a part of the community.”

The chief was told that it would be a cultural movie, similar in style to Silence (2016), Scorsese’s historical drama about two 17th-century Jesuit priests (Andrew Garfield and Adam Driver), who try to contact their former teacher hiding somewhere in Japan, a land where Christians have gone underground because of violent persecution by the ruling lords.

Like Killers Of The Flower Moon, the adaptation of Shusaku Endo’s 1966 novel of the same name reflects the auteur’s fascination with ideas of divinity, redemption and cruelty.

It bombed at the box office, but is now considered one of Scorsese’s best films.

However, Chief Standing Bear was concerned about Scorsese’s habit of depicting violence for his latest passion project.

At an early screening for members of the Osage community, Chief Standing Bear noted that among them were descendants of the murder victims.

That was when he was gripped by worry. Had he erred in giving the film-maker creative leeway?

“I thought to myself, ‘What must it be like to see your grandfather shot in the head on a big screen?’ That’s a pain I had not considered. I fell short on that. The trauma is something we all have to work on. There are issues to this day.”

• Killers Of The Flower Moon opens in cinemas on Thursday.