Hannah Baxter pictured with her 'main man', son Trey in a beach snap

A mother of three children who were killed by their father when he set the family car alight has died in hospital.

Hannah Baxter, 31, survived the initial inferno, which killed Aaliyah, six, Laianah, four, and Trey, three on Wednesday morning.

She was taken to the Royal Brisbane and Women's Hospital after the blast with burns so severe witnesses said her skin was peeling off her body as she screamed in agony.

By Wednesday afternoon her condition had deteriorated. She was pronounced dead early this evening.

Her estranged husband, Rowan Charles Baxter, also survived the initial blast but stabbed himself in the chest beside the burning car as neighbours desperately tried to free his children.

The 42-year-old former NRL player jumped in the car as Ms Baxter strapped the children in to do the school drop off.

She was parked down the road from her parents home in Camp Hill, in Brisbane's south-east. She and the children had reportedly been staying there since separating with Baxter about two months ago.

The couple were reportedly working through a nasty custody battle after their separation.

Witness Andrew Sinclair said he will never forget seeing Ms Baxter writhing in agony as her body burned.

'The look of hurt looking straight at me, and seeing her clothing being burnt with her skin coming off her body, it was an awful thing to see,' he said.

Pictured: Rowan and Hannah Baxter. Hannah died in hospital after suffering serious burns

Baxter's New Years' Day post: The killer former NRL player brought in the new year with this post of his children in the shallows. 'Goodnight ratbags always in my heart,' it was captioned

Bodies were seen being loaded into the back of a funeral van on Wednesday afternoon, the family's burnt-out Kia Sportage can be seen in the background being examined by police

Flowers and a dolly were placed on a grassy patch near where the tragedy unfolded after three young children were killed

Another neighbour said she was entirely conscious and aware of what had happened.

'Skin was peeling off her, and she held her hands up... bits were hanging off. It was really quite horrific,' the man said.

Aaron Snell, another neighbour who witnessed the tragedy, said he initially thought he was watching a road rage attack before he realised the gravity of the situation.

By the time he reacted, Ms Baxter had escaped from the car and was rolling on the footpath in an attempt to smother the flames.

A Good Samaritan was also trying to hose her down to stop the fire.

Witnesses said they heard her shouting 'he's poured petrol on me' at the time.

Baxter was also still alive.

He was across the road, but returned to the car to salvage a knife. He then stabbed himself in the chest, Mr Snell said.

Mr Snell, who is trained in CPR, said he was trying to assess whether he could perform it on Baxter because he was 'just in all matter of states,' he told The Courier Mail.

Queensland Police officers were called to a family violence incident allegedly involving the couple just last month

Neighbours said all they could see was thick, black smoke - followed by flames reaching into the air

Wreckage: This is the white Kia Sportage SUV that went up in flames in Camp Hill, in Brisbane's south east, at about 8.20am on Wednesday

'As I came to the front after calling Triple-0, I saw her (Hannah). She was smoking, her body was smoking and on fire,' Mr Snell said.

By this point, others were on the scene and trying to put out the fire in an attempt to save the children, who were still trapped inside.

Mr Snell believes Baxter attempted to stop them helping his children in his final moments.

'He was so angry and just going absolutely crazy. It appeared like he wanted [the car] to burn,' he said.

Baxter, an ex-New Zealand Warriors player, stabbed himself with a knife during the horrific attack on his family.

The couple had recently separated and shut down the business they ran together, Integr8 Fitness, based at Capalaba.

The family business: Rowan Baxter with Hannah Baxter and their three children pose in front of the company logo

Baxter flooded his Facebook site with photos and videos of his children, describing them as 'my world'

BRISBANE MURDER-SUICIDE: HOW COWARDLY RAMPAGE UNFOLDED JANUARY, 2020 Queensland Police officers are called to a family violence incident that allegedly involved the couple. WEDNESDAY FEBRUARY 19 - EARLY MORNING: Rowan Charles Baxter, 42, is spotted filling a jerry can with fuel at a local service station. 8.20AM: Baxter dives into his estranged wife Hannah Clarke's white Kia Sportage as she was preparing to do the school drop off on Raven Street, Camp Hill, a wealthy suburb of Brisbane. He douses Ms Clarke, 31, and their three children - Aaliyah, six, Laianah, four, and Trey, three - in petrol and sets the car alight. Neighbours hear an explosion which sounded like a 'gas bottle' blast. At least four explosions followed. Baxter grabs a knife from the SUV and stabs himself in the chest. He tries to stop neighbours from saving his wife and children before dying in the street. Ms Clarke escapes the burning car and screams: 'He's poured petrol on me.' Horrified witnesses see her skin peeling off her body. One heroic neighbour hoses her down in an attempt to save her life and suffers burns himself. She is rushed to Royal Brisbane and Women's Hospital in a critical condition. WEDNESDAY NIGHT: Ms Clarke dies in hospital from the horrendous burns she suffered in the quadruple murder suicide. Advertisement

Police attend the scene of a car fire which claimed the lives of an entire family of five

'T-R-E-Y, love you to the moon in back', Rowan Baxter wrote - before he was suspected of killing his children and himself. A friend, Joey Abraham, told him 'chin up, everything will work out'

A police photographer is pictured at the Baxter home in the neighbouring suburb of Carindale following the horrific inferno in Camp Hill

In recent months, Baxter flooded his Facebook site with photos and videos of his children, describing them as his 'world'.

'T-R-E-Y, love you to the moon and back,' he posted six days ago.

A month earlier, he captioned a post: 'Goodnight my babies, Daddy loves you.'

But in disturbing footage also shared to his social media, Baxter 'roughed up' his kids to toughen them up.

He slammed his youngest, Trey's, head into the corner of a bed multiple times and pretended to strangle him while holding him in a headlock in video shared online.

The comments section of the video, as well as a photo where he throws Trey high into the air, have been flooded by strangers who claim the posts show a 'blatant disregard' for the children's safety.

Inferno family: Hannah and Rowan Baxter, with their three children (from left to right) Aaliyah, Laianah and Trey

Hannah Baxter survived the initial inferno, which killed her three children, Aaliyah, six, Laianah, four, and Trey, three on Wednesday morning

The blaze occurred in Camp Hill, described as an upmarket, family-oriented suburb in Brisbane's east

Weightlifting friend Joey Abraham wrote to Baxter four days ago: 'Chin up brother everything will work out just hang in there my bro.

'A lot of people care about you and the situation you're facing.'

A reeling Mr Abraham told Daily Mail Australia after the incident: 'Rowan was in a real bad place there for a bit because of the separation.

'If you knew Rowan when he at his best and to see him like last week then you know how far he'd fallen.

'He was just a shadow of the person he used to be.

'It's just unbelievable that he could do this.

'They were beautiful kids, they were a beautiful family.'

Queensland Police officers were called to a family violence incident that allegedly involved the couple just last month, The Courier-Mail reported.

But the family were not involved in any Family Court or Federal Circuit Court proceedings.

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A policeman is pictured at the brick-and-tile Carindale residence where the father and his family had lived. A friend described the Baxters as a 'beautiful family'

Burned-out wreck: Rowan Charles Baxter, 42, and his three children, Aaliyah, six, Laianah, four, and Trey, three, all died when the family's white SUV was set alight at Camp Hill

Brisbane's Lord Mayor Adrian Schrinner rests a teddy bear at a growing vigil in Camp Hill

The police crime scene in Camp Hill as of Wednesday afternoon

Sheets were still left on the line out the back of a home once occupied by the Baxter family