Braydon Worldon's body was discovered on the side of a road in Wantabadgery in December 2018 by a passing motorist.

The 15-year-old's death occurred a few hours after he had celebrated his birthday.

Police have now revealed that they believe Braydon was hit by a heavy vehicle on River Road, and that the driver knows what they have done.

That information and more will be presented at a coroner's inquest in March.

Speaking directly to the driver, Riverina Police District Crime Manager, Detective Inspector Adrian Telfer, said "come forward".

"This has been a very unfortunate incident for Braydon and his family," he said.

"Please, please come forward. Do the right thing ... this investigation is never going to go away."

About 1.30am on December 19, 2018, emergency services were called to River Road, Wantabadgery, about 40 kilometres east of Wagga, after a passing motorist saw a body on the road.

The driver stopped to render assistance and discovered it was the body of a teenage boy who has since been identified as Braydon.

Detectives from Riverina Police District established Strike Force Dunstable to investigate the circumstances surrounding the death.

The teenager was last seen alive during the evening of December 18, and police suspect he was hit by a heavy vehicle, fitted with a bull bar.

Police are seeking any information from the public in relation to heavy vehicles that use River Road and those that may have been in the area on the night of the incident.

Braydon's grandmother June Worldon spoke with The Daily Advertiser about what a beautiful boy her grandson was.

"I miss him so much," she said. "Look at the grass out there, he would be here mowing it for me.

"He always thought 'Oh, Nan might want something done' and he was a good boy."

Mrs Worldon said she had fond memories of what Braydon was like, joking that he could easily eat six or eight slices of bread in one go.

"I always made sure to have something for him," she said.

"He spent a lot of time here with me."

Every day, Mrs Worldon asks herself: "How could someone do this and not come forward?

"Even if you thought you hit a kangaroo, why wouldn't you check?

"The police said his injuries were so horrific they might not have been able to help him, but why wouldn't you stop?"

Braydon would have been 17 by now, and his grandmother often wonders what he would be like if he was still alive.

"Where would you be now, mate," she said.

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"He wanted to be a shearer, and I said 'Well, get a good shearing contract, and you can go right around Australia with that'.

"He wanted to buy a house to live in, and I told him to buy local, and he can always come home."

Mrs Worldon said she cannot believe a local person would be responsible for her grandson's death, adding they would have heard of it by now.

"Whoever it is, please just come forward," she said.

"We just want the truth."

Inspector Adrian Telfer, said police are continuing to be thorough in their investigations.

"We are continuing to follow up on information provided by the public as well as our own avenues of investigation," he said.

"We want to be able to provide answers to Braydon's mother, Crystal, and the rest of his family regarding the circumstances of Braydon's death.

"Any information that can be provided by the public is invaluable."

Inspector Telfer said officers are confident that the person responsible knows they hit a person.

"Very shortly after this terrible incident, we had been very public about this and that it was a collision involving a vehicle that left the scene," he said.

"So we are fairly satisfied that the person involved would know that a 15-year-old was killed."

Inspector Telfer said there is nothing to suggest that speed was involved.

"We do believe the pedestrian was on the road at the time," he said.

"We can't conclusively say the exact time that this occurred, but we believe it was in the vicinity between 9pm the 18th and 1am on the 19th.

"There's about a four-hour window there, and obviously traffic is very minimal in this area."

Inspector Telfer said it is essential that anyone who has information comes forward because even the most minor detail can help piece the puzzle together.

A coroner's inquest into the circumstances surrounding Braydon's death has been listed for hearing at Wagga Coroners Court on March 30.

"We have been gathering information over the last couple of years since the night of the incident," Inspector Telfer said.

"All that information will be presented to the coroner and they will make a determination."

Braydon's mother, Crystal Worldon, also pleaded with the person responsible for killing her son just to admit what they have done.

"Please, we want to know the truth," she said.

Previously, Ms Worldon had told The Daily Advertiser that the second Braydon was born, she loved him with all her heart.

"As a baby, you just never wanted to stop cuddling him," she said.

"You never wanted to put him down.

"Everyone wanted to hug him and would fight to hold him."

In 2019, Ms Worldon said Braydon was a cheeky rascal but was lovable and kind and not afraid to stand up for what was right or who needed it most.

"He helped a lot of kids out that he went to school with at Wagga High," she said.

"There was one girl, she has cerebral palsy, and she was getting picked on, and he would stand up for her.

"We always taught him that it didn't matter what someone has got, you treat them like anyone else, and he would always follow that.

"I'll remember Braydon for everything, his personality and his cheekiness, I really miss that ... I wish I could tell him I loved him."

Anyone with information about this incident is urged to contact Crime Stoppers or 1800 333 000 or at www.nsw.crimestoppers.com.au.