New Zealand firefighting pilot Ian Pullen lay mortally injured on the side of a country road after being struck by a car when driver Joshua Knight and passenger Nicole Mason got out, walked over to have a look at the hero father and left him to die alone.

Neither went to authorities, with Knight even crashing his Toyota HiLux into the Singleton Rugby Park fence twice in a bid to camouflage the damage to the vehicle, while Mason only told one person – and then made threats via a third party once she was outed as knowing what happened to Pullen.

But even as Knight and Mason learnt their fate in Newcastle District Court on Tuesday, Pullen's devastated family still don't know exactly what happened on that spring morning in 2018.

"Only four people know what happened that night and they are not saying," Pullen's devastated wife Vicki Pullen said outside court.

Knight, now aged 31, and Mason, 32, had been initially charged with the murder of Pullen before the charge was withdrawn, with Knight facing one count of failing to stop and assist following impact causing death and Mason facing one count of concealing a serious indictable offence.

Ian Pullen, a firefighter pilot from New Zealand, was found dead by the side of the road in NSW's Hunter Region in 2018. Image / Supplied

The downgrading of the charges came after a forensic pathologist reported that Pullen would have died from the injuries he suffered when struck by the car within 30 minutes of the collision whether he received medical treatment or not.

But exactly what occurred after 4am on September 29, 2018, may never be known, with Judge Roy Ellis noting when sentencing Mason that her concealment meant any suggestions relating to illicit drug user Knight's sobriety or manner of driving at the time of the collision could never be tested.

"There is no doubt that his conduct in simply driving off and leaving this man seriously injured on the side of the road was morally reprehensible," Judge Ellis said in sentencing Knight.

Knight could be out of prison in just under a year after being sentenced to a maximum of three years and two months in jail with a non-parole period of two years and four months backdated to February 24, 2021.

Mason could be released on August 18 after being sentenced to a maximum of 14 months with a non-parole period of seven months, backdated to January.

Knight, who appeared via audio-visual link from Shortland Correctional Facility at Cessnock, stared at the ground as Pullen's devastated wife Vicki and mother Gillian read emotional victim impact statements to the court.

The Pullen women, along with Pullen's son Cody, had travelled from New Zealand and were hoping to look Knight in the eyes.

"You didn't just kill Ian Pullen the day you ran him over, you killed a major part of me," Vicki Pullen said,

Knight's barrister Paul Rosser QC told the court that although his client's behaviour was "an act of bastardry", "despicable" and "callous", he was only guilty of not stopping to help an already dying Mr Pullen and had not been found responsible for his death.

Pullen had arrived in Australia to help fight bushfires and had been drinking at a Singleton pub before being seen drunk and stumbling back to his accommodation at a caravan park in the Hunter Valley town.

He was seen by a resident lying down on the road before the collision, although his injuries were consistent with being struck while standing up.

Pullen was just 20 metres from the entrance to the caravan park when he was struck by the HiLux being driven by Knight, who was suspended from driving at the time.

Joshua Knight has been charged with murder, dangerous driving occasioning death and failing to stop and assist after vehicle impact causing death. Picture / Facebook

A resident who lived directly across from the caravan park would tell police they woke to a loud noise at about 5 am and about five minutes later, heard a male voice coming from the street say "oh f--k".

Pullen was found about 20 minutes later. Knight would smash his car up two days later in a bid to disguise the damage from the collision with Pullen.

He was arrested 16 months after Pullen died but was not charged over the incident for a further eight months.

The court heard he had not shown remorse, had continued to use drugs inside jail and was at a high risk of reoffending.

Vicki Pullen – who was forced to battle cancer while grieving the loss of her husband and lost the family home because her husband was the primary money-earner – said outside court that justice had not been served."

"It's a system that's let families of victims down," she said.

"It's been horrendous. We have been waiting for them to come forward and then they come forward and then they virtually get away with it."

She later added: "He didn't do anything to them. And he's the one that suffered from it."