The man who portrayed Port Arthur mass murderer Martin Bryant has won the Best Actor award at the annual Cannes Film Festival.

The film Nitram, about the events of Australia's worst massacre that killed 35 people, was accused early of possibly glorifying the killer.

But critics were stunned by the intimate family drama about mental illness that exploded into the headlines in 1996.

The film ends in the seconds before Bryant starts shooting at the former convict colony.

With the memory of the massacre still raw, actor Caleb Landry Jones, 31, said 'it was very evident that people were going to be angry'.

'Some people probably pegged the film to be a certain kind of movie,' he said.

'But it is a very sensitive piece and https://ohiocentralintake.org/ very respectfully made.' 

Being Texan helped with his role: 'The film is in many ways about the Australian male.

I found a lot of similarities with Texas. So I knew what that was.'

He spent three months trying to get under Bryant's skin.

'I really worked on the dialect for two months in Texas. But I arrived a month before we began shooting and if it wasn't for that I think I would have failed miserably,' he said.

As he accepted his award, Jones said: 'I can't do this, I am going to throw up.'

'Thank you to the jury ...

f**k. Thank you Justin ... f**k. I can not do this. I am so sad that I can not do this. Thank you so much. Thank you so much!'

Due to the sensitive subject nature of the movie, producers chose to film in Victoria instead of Tasmania where the tragedy occurred, the reported at the time of production in November. 

The film will not depict the killings, but will instead focus on Bryant's life before his murderous rampage in an attempt to understand how the atrocity occurred. 

The publication also reported that the film will not name Byrant, and will also assign fictional names to other key characters. 

Australian stars Judy Davis, 66, and Anthony LaPaglia, 62, took on the role of Bryant's parents.

Actress Essie Davis, 51, portrayed Tattersalls lottery heiress Helen Harvey, who was a companion of Martin's.  

His trail of destruction took the lives of 35 adults and children, injuring another 23, and prompted historic gun control legislation under the John Howard government.

Bryant pleaded guilty to 72 charges including murder, attempted murder, causing grievous bodily harm and arson.

On November 22, 1996, more than seven months after the massacre, Tasmanian Supreme Court Chief Justice William Cox ordered Bryant serve 35 life sentences without parole.

Bryant has never offered an explanation for his actions.

Still, there is speculation, including from investigators, that his murders were sparked out of retribution for grievances and others were collateral damage. He will die at Hobart's Risdon Prison.