In a panic, he called his mother and enlisted her help to remove Ms Dixon's lifeless body from the road.
But the pair left the dead Indigenous woman's dismembered leg on the Northern Territory's Stuart Highway, triggering a massive police investigation as well as their eventual arrest.
Mason, 25, pleaded guilty to hit and run and interfering with human remains while his mother, Deborah Mason, 51, pleaded guilty to interfering with human remains and perverting the course of justice in the NT Supreme Court on Tuesday.
On May 30, 2022, Ms Dixon got off the bus at Palmerston, south of Darwin and began walking towards the city.
Joshua Mason hit her at about 8.30pm as she staggered across the highway.
Deborah Mason then helped collect, move and conceal the woman's body in bushland 15km south of the collision site.
Her body was later found partially buried in scrub in Bees Creek on June 1 after the pair were arrested and Deborah Mason took detectives to the grave.
A traveller driving on the four-lane highway linking Darwin to Alice Springs and Adelaide had spotted the partial leg.
The court heard that when Mason eventually admitted the hit and run to police, he told them: "It's my life, it's my mum's life, and because a drunk idiot wants to walk across a dark road at night time, my life is over."
The maximum penalty for misconduct with a corpse in the NT is two years' imprisonment. Destroying evidence and attempting to pervert the course of justice carry potential three and 15-year terms respectively.
More than 30 members of Ms Dixon's family filled the courtroom, with some travelling from Alice Springs to watch the pair enter their pleas.
Many were too emotional to stay in court and had to be excused as the details of Ms Dixon's body removal were read out.
Other family members read out tearful victim impact statements, including her cousin Carol Dixon.
"My heart has been ripped out of my chest," she said as she stared down at the pair in court.
"No one should ever hear what I have heard about my loved one ... you did the wrong thing."
Outside court, Ms Dixon said she hoped her cousin would be remembered as a "beautiful soul".
"I think about her every day," she said.
Joshua Mason will remain in custody and his mother's bail has been extended until the matter returns to court on October 12.
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