A Brisbane mother who was set alight with her three young children “did everything she could to protect” them from her estranged husband, a friend says.

Hannah Baxter, 31, was pulled alive from the driver’s seat of the family car as it was engulfed by flames on a Camp Hill street about 8:30am on Wednesday, during what should have been a routine school run.

Her children — Lainah, 6, Aaliyah, 4 and Trey, 3 — all died inside the car.

Ms Baxter died hours later in hospital.

Her estranged husband and the children’s father, former Warriors rugby league player Rowan Baxter, allegedly poured petrol on his family in a suspected domestic violence incident.

Hannah and Rowan Baxter with their three children Lainah, Aaliyah and Trey. (Photo: Facebook)

Police said he was in the front passenger seat but made it out of the burning vehicle.

He died with self-inflicted wounds on the footpath, police said.

Friend Caitlin Langford said Ms Baxter was “just the most beautiful woman”.

“She was kind, and strong, and lit up any room,” she said.

“She was the most beautiful mama to her babies and the most inspirational role model.”

Hannah’s brother, Nat Clarke, posted a tribute to his sister and her children on Facebook.

“R.i.p you beautiful souls,” Clarke wrote. “I had my sister nephew and 2 nieces taken from me in the worst way possible … I will forever love you all”.

Meanwhile, mourners have visited the street where the children died to lay floral tributes and pay their respects.

Facebook fundraising page set up by Hannah’s sister-in-law Stacey Roberts has so far raised more than $52,000 for funeral costs, with thousands of dollars coming in each hour.

Hannah’s parents needed support, Roberts posted, and had “exhausted themselves” trying to help Hannah, who left her partner before Christmas last year.

“For all those who knew Hannah or had even just met her once would know how much of a beautiful soul she was, her children [were] her life.”

Hannah and Rowan Baxter ran a fitness business at Capalaba for about five years. Ms Baxter was a champion in trampoline sports and specialised in kids and “Mums n’ bubs” classes.

The gym shut its doors late last year.

Friends of the couple told the ABC that signs of the Baxters’ lives unravelling were there.

Ms Baxter had moved out with the children, and Mr Baxter, months away from his 43rd birthday, was left living alone in the three-bedroom Carindale home the family had shared.

Friends said problems in the marriage had been visible for some time.

“She loved them so fiercely and she was doing everything she could to protect them,” Langford said.

For the months after the separation, Mr Baxter peppered Facebook with messages wishing his children good night, posting pictures of them cuddling together, and telling them he missed them.

A fundraising page has been set up for Ms Baxter and the children’s funeral.

Police are expecting to give more details of their investigation into the suspected murder-suicide this afternoon.

Mr Baxter, born in New Zealand, proclaimed he was “one of the top fitness coaches in Brisbane”, and his expertise was once bolstered by a video testimonial from rugby league star Sam Thaiday.

But it was another online video of Mr Baxter that provoked the attention of many in the wake of the tragedy.

Last month, he posted a video on Facebook of him play-fighting with his children.

He responded to their playful “attacks” with practised demonstrations of the kind of headlocks used in mixed martial arts, and laughed out loud after slamming toddler Trey’s face into a mattress.

“Sweet dreams my babies xo Love you to the moon and back #nowords #dad #myworld”, he posted.

Others read something more sinister into the muscular man’s rough-housing with the young children.

In the wake of yesterday’s tragedy, more than 700 people piled on to Mr Baxter’s page to post mostly damning comments under the video.

Arguments raged about whether his handling of the kids in the video represented some kind of warning sign.

The suspected killings of Hannah Baxter and her children echo a series of disturbing cases more than four years ago that thrust the protection of women at risk from former partners onto the state political agenda.

The public outcry in response to a cluster of highly-publicised homicides in 2015, including Tara Brown and Karina Lock, prompted moves to overhaul police and government responses to family violence.

The Palaszczuk Government fast-tracked recommendations from Quentin Bryce’s Not Now, Not Ever report.

– ABC, AAP