The mother of a young man killed in a garbage truck tragedy in Western Sydney is demanding answers from police, saying she believes her son’s death “could have been avoided”.

Nathan Hearne, a 22-year-old bar worker, was hit by the truck outside a restaurant on Luxford Rd in Mount Druitt about 2.20am on Thursday.

WATCH THE VIDEO ABOVE: Mother questions police after son’s tragic death

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Paramedics desperately tried to save him, but he died at the scene.

His mother, Leanne Whelan, told 7NEWS she first became concerned after seeing a Facebook post showing sheets at the scene of the tragedy — without realising it was her son underneath.

She later tried to call Hearne before contacting police, but said officers would not give her any information over the phone and told her someone would be in touch.

“I broke down when they said that they would be in contact. That, to me, basically told me, but in my mind, I didn’t want it confirmed,” Whelan said.

“I was trying to push it off because Nathan is 22, the report said he was 21.”

Hearne once donated bone marrow to help his sick brother. Credit: Facebook

It was only when Whelan’s partner went to the police station that the family received confirmation, with a detective speaking to her over the phone.

“(I felt) heartbreak, empty,” Whelan said, struggling to hold back tears. 

“I’ve lost my son. He’s my pain in the butt.

“I’m expecting him to ring me and ask me for 20 bucks to see what he’s cooking.”

“It just doesn’t feel like he isn’t here.”

‘Could have been avoided’

A critical incident investigation has been launched after police revealed Hearne had attended the rear of Mount Druitt Police Station twice that evening and interacted with officers.

Whelan said Hearne, who had high-functioning autism, had been drinking with a friend and the friend’s girlfriend at a pub on Wednesday night.

She said she was later told by a detective that her son had been “a bit aggressive” during his interactions with police.

About 1am, Hearne called his sister while “very agitated” and told her he was scared of police, Whelan said.

Police said Hearne had interacted with police twice in the hours before his death. Credit: Supplied

The grieving mother now wants to know why more was not done to help him.

“Where’s the duty of care?” she said.

“I want to know why you didn’t put him in a cell for the night or send him home or call someone.

“He could have been saved.”

Whelan said the family still knew little about exactly what happened in the hours leading up to Hearne’s death.

“All we’ve been told is that he was hit by a truck and that’s it,” she said.

“I’m ropable.

“I’ve lost my son at the cost of their ignorance, their arrogance.”

Leanne Whelan wants to know why more was not done to help her son. Credit: 7NEWS

Whelan said she also wanted answers about why the family had to chase police for confirmation of Hearne’s death.

“Why didn’t someone come to my door and tell me what had happened?” she said.

Police sources have told 7NEWS Hearne displayed no obvious signs of distress and they had advised him to head home.

Selfless act before death 

Amid her grief, Whelan remembered her son as a larger-than-life 22-year-old who loved his family, his girlfriend and making people laugh.

“He liked to be loud. He liked to drink. He really liked his girlfriend. He liked the expensive colognes,” she said.

“He was a typical 22-year-old kid.”

Hearne had been working at a bar and had previously worked in landscaping.

“He loved everyone,” Whelan said.

“He loved his brothers. He was a big kid. He loved kids.

“Even from a young age, he’d go into a shopping centre and he’d be pulling faces at babies.”

Hearne’s mother Leanne Whelan said he loved his brothers. Credit: Supplied

That love for his family was demonstrated last year when his younger brother Stevie needed a bone marrow transplant.

Stevie and another brother, Colton, have Familial Hemophagocytic Lymphohistiocytosis type 5 (FHL-5), an extremely rare inherited immune disorder, according to a GoFundMe set up to support the family.

When Stevie’s father became too unwell to donate bone marrow, Hearne stepped in.

“He had the biggest heart,” Whelan said.

“He loved his brothers. Every time he was there, he wanted hugs.”

Stevie has responded well to the transplant, while Colton is currently in hospital recovering from the same procedure.

Neither boy has yet been told that their brother has died.

“The older two we’ve told. Stevie we haven’t told yet, and Colton is not well enough to be told yet,” Whelan said.

She said telling Hearne’s other siblings had been one of the hardest moments since his death.

A critical incident investigation is underway. Credit: 7NEWS

The 31-year-old garbage truck driver was uninjured and was taken to hospital for mandatory testing.

A critical incident investigation team from Riverstone Police Area Command will investigate the circumstances surrounding the incident.

The investigation will also be independently reviewed by the NSW Police Professional Standards Command and overseen by the Law Enforcement Conduct Commission.