UPDATE: A man has been charged with murder over the death of 23-year-old Australian man Wade Still.
The young father-of-two was discovered by a taxi driver on the roadside at Whitebridge near Newcastle at about 1am on Monday. He had suffered extensive burns and died as he was being flown to hospital.
A 35-year-old man was charged with murder on Tuesday, with police confirming the charge late on Tuesday night.
"The two men were alleged to be known to each other," a statement from police said on Tuesday night.
James Madden, the taxi driver who found Mr Still lying on the side of the road completely covered in burns, said the young man spent his final minutes screaming in pain.
"He was screaming at the top of his lungs. 'I'm dying, I'm dying' he was screaming. It was terrible," Mr Madden told Seven News Monday night.
"He was very burnt and blistered, there was very little clothing left on him."
The taxi driver contacted emergency services and Mr Still received treatment at the scene. However he died en-route to Sydney's Royal North Shore Hospital, where he was being taken because of the extent of his injuries.
It is understood the 23-year-old from Lake Macquarie had recently been released from prison after being jailed for assaulting paramedics.
Police from Lake Macquarie Police District established Strike Force Yaraandoo to investigate the circumstances surrounding the incident.
The 35-year-old was refused bail will face Newcastle Local Court on Wednesday.
EARLIER: Mr Still was jailed last September for punching and kicking emergency workers who were trying to take his partner to hospital as she entered labour.
The young father's partner Paige Millan said she woke to a phone call from one of his friends early on Monday.
"His poor kids are going to be broken," she told reporters in Newcastle on Monday.
"I want (the culprit) to come forward and pay for what you've done."
Police spent Monday searching the area for a weapon and say the death is suspicious.
"We're certainly not treating this as a casual event and the inclusion of the Lake Macquarie command, homicide squad and Newcastle city reflects the gravity we are taking," Superintendent Danny Sullivan told reporters on Monday.
Police are investigating several lines of inquiry and are not ruling anything in or out, he added.
"The real key message here is that anybody with any information, no matter how small, to contact crime stoppers."
Investigators urge any locals who have dashcam footage or saw suspicious activity to contact them immediately.
Dashcam footage has already emerged of a woman seen walking along that same stretch of road late on Monday night.
Anyone with information about this incident is urged to contact Crime Stoppers on 1800 333 000.
- with AAP