Luke Shaw was found unconscious and dying in a Mildura street 10 years ago on Wednesday in what is believed to be a hit and run. His family had to turn off his life support in hospital the next day. On Tuesday, Victoria Police announced a $100,000 reward for information leading to an arrest and conviction over the death.

Ten years after a young man was killed in Mildura, it's the crime scene that still sticks with investigators.

The telltale pieces of a hit-and-run accident – like paint chips or broken glass – weren't there. There were also no witnesses, apart from the ones that have kept a heavy secret.

Really, all they had was 21-year-old Luke Shaw – one of 11 children from nearby Red Cliffs – and blood stains on a bitumen road that had seeped from a wound on his head.

"There's nothing apart from Luke's injuries and Luke himself," Detective Inspector Bernie Rankin said.

"That's really what we're working with."

What happened outside that scene in Ninth Street in the decade that followed were red herrings fuelled by rumour.

First, there was the one about the young woman whose brand-new car turned up at a panelbeaters with a dint on it about the same time Luke was killed. Police would later find out she was acting evasively because she was terrified her parents would find out she had been drink-driving.

Then there's the other rumour that has dogged the investigation the longest – the one that Luke was assaulted with pool cues. That one spawned from two different sets of facts; that there had been an assault with pool cues, but on a completely different victim, and there had been a verbal fight that had involved Luke.

Luke had gone out drinking with his brother at O'Malley's Irish Tavern on the night he was found and had an altercation over a former girlfriend, but that, police said, had been resolved by the time he left the pub.

"We don't believe that argument is connected with his death. We've had a fairly close look at the people involved in that," Inspector Rankin said.

It's the 50 minutes between when Luke was last seen – standing on the corner of Deakin Avenue and Ninth Street – to when he was found unconscious at 3.23am by a security guard that is the yawning gap in the investigation.

But as little help as the crime scene was, Luke himself provided clues that have built a solid theory that he was most likely picked up in a vehicle by someone he knew.

"His injuries do suggest to investigators that he hit the ground forcefully ... we believe he has fallen from or [been] thrown from a vehicle," Inspector Rankin said.

"And we're certain there are people still living in Mildura now that know what happened on that particular night. He comes from a large family and they're grieving for him, they'd like to know what caused his death."

As much as rumours took the police investigation on twists and turns, it barely compares to what it has done to Luke's family – his mother Jennifer, father Glenn and 10 brothers and sisters.

Luke, Jennifer said, was the scallywag of the family – popular, cheeky and a bit wild – but he worked hard on an orchard with his dad and craved having a family of his own.

A lot of the information his family receives about his death comes through the Facebook tribute page that Jennifer manages. It varies from the ridiculous – like that his 11-year-old brother had hit him with a baseball bat – to theories she just can't shake.

"We have had so many names put in the pot and most of what comes in is about an assault," she said.

"So instead of having an idea of what happened, you have this void ... and your head goes around and around."

Jennifer can't get rid of a senseless guilt she feels, the never-ending "What if I did something different?" feeling and her children, the youngest of whom were robbed of memories of their big brother, detest going into town.

"I think it's the security. Home's safe; everything else isn't safe anymore," she said.

The Shaws are well-known in the region, their name synonymous with the local fire brigade where Glenn and four of his children, including Luke, had been members. And Jennifer says,  it feels like everyone knows who they are because of what happened to Luke and the ones that truly do know, won't give them the answer.

The reward could be their last chance to unearth the truth, she says.

"I can't sleep now having a dead child, how can they sleep knowing they're responsible for one?" she said.

Anyone with information is urged to phone Crime Stoppers on 1800 333 000 or go to crimestoppersvic.com.au.