The 33-year-old bike rider died on Thursday afternoon, after the youths' stolen black BMW X5 hit his motorcycle at the junction of Glenburnie Road and Orient Avenue in Mitcham.

According to Detective Inspector Stuart McGregor from the major collision investigation unit, the motorbike rider had multiple fractures and burns to 50 per cent of his body.

The crash happened about 4.15pm on Wednesday.

About 10 kilometres away, and about 15 minutes after the crash, a family in Haideh Place, Scoresby had their home invaded and their white Toyota Camry sedan stolen after the four youths ripped open their front door and took the keys.

The stolen Camry was found dumped and burnt out in Brundrett Road, Narre Warren North, early on Thursday morning.

The four young men, aged about 17, are now believed to be in a Hyundai.

Detective Inspector McGregor said the motorbike rider was a family man and sheet metal worker from Mitcham.

He had family overseas who police were trying to contact.

Detective Inspector McGregor said the driver of the BMW failed to give way at an intersection and ploughed into the motorbike, dragging the rider 85 metres along the road.

It did not appear they were excessively speeding at the time.

Police are investigating what the youths had done prior to the crash, with the BMW stolen in late October, and other crimes linked to a similar car having since been reported.

It is also unclear what the men did between the home invasion and burning out the Toyota.

Detective Inspector McGregor said there was no description of the young men, other than that they were wearing street clothes and at least one was Caucasian.

"It's just people who play a game, they play the game of stealing cars and driving fast," he said.

"It's like they're playing a video game. And unfortunately this is a real life game.

"And unfortunately people get hurt. And what happens is people go to jail.

"And that's going to be the result of this: someone got hurt, and these people are going to go to jail."

Premier Daniel Andrews said it was completely unacceptable to drive off rather than stopping to help after an accident.

"If you're involved in one of those terrible accidents you need to render whatever assistance you can," he said.

"It's cowardly, it's shameful not to."

'We thought it was a safe, quiet neighbourhood'

John and Kerryn, who've lived in Haideh Place for 26 years, were working in the garden on Wednesday afternoon and had no idea their home had been invaded.

The first sign that something was wrong was when Kerryn saw the mangled front security door with the bottom left-hand side wrenched up.

Her first, panicked thought was for the safety of her 21-year-old daughter who was in her room.

'I just thought, 'oh my God, Sarah'," Kerryn told Fairfax Media.

"I didn't know what danger she was in, if someone was still in the house. I crawled in under the door, screaming to John.

"When you're a mother it doesn't matter, you've got to get to them whatever it takes."

Luckily none of the family encountered the youths who quickly grabbed a phone, a wallet and car keys from the hall stand.

They made off with John's Toyota Camry sedan.

"We thought it was a safe, quiet neighbourhood," John said. "Nothing like this has ever happened here."

'I knew something was wrong'

Speaking to Fairfax Media on Thursday, witnesses to Wednesday afternoon's fatal hit-run said the youth's BMW was speeding moments before it ploughed into the motorcycle, dragging it several metres before it burst into flames.

Nearby residents rushed to his aid and saw the gang fleeing the scene.

One resident used a hose to douse the motorbike, while others tipped buckets of water over the rider and then wrapped him in a blanket, a witness said.

"I heard a very loud noise, a big crash," an Orient Avenue resident, who did not wish to be named, said.

"I wasn't sure what happened but when I heard more noises I knew something was wrong."

She went outside in time to see a black car reversing quickly from the crash and then speeding away down Glenburnie Road. She did not see those inside.

A woman shouted out the registration of the car, as the neighbour looked up Orient Avenue and saw the flaming wreckage.

"It was a big, big fire. I didn't even know it was a motorbike, I thought it was a car," she said.

Once the flames died down, she saw the rider lying in the road. He was not moving, but he was alive, and being comforted by those who had rushed from their homes.

"They were just saying the ambulance is coming, it will be OK," she said.

The motorcyclist, who is from Mitcham, was taken to The Alfred hospital where he remains with life-threatening injuries.

The BMW was later found dumped on EastLink in Scoresby.

Police say the four occupants of the BMW then committed the aggravated burglary in Haideh Place.

Major collision investigation unit detectives are keen to speak to any witnesses who saw the BMW in the Mitcham or Scoresby areas.

The hit-run is Melbourne's second this week. On Thursday morning a 41-year-old woman was arrested over a 13-year-old girl who was knocked off her bike in Coburg .

Anyone with information should call Crime Stoppers on 1800 333 000.

With Benjamin Preiss