Ms Clarke was yelling and crying while talking to off-duty paramedic Stephanie Ring, who came across the burning car in Brisbane's Camp Hill minutes before firefighters arrived on February 19, 2020.
The 31-year-old mother was leaving her parent's home with children Aaliyah, six, Laianah, four, and Trey, three, when estranged husband Rowan Baxter got in holding a jerry can and knife.
Ms Clarke said Baxter "squirted petrol" then threw a lighter in the car, Ms Ring told the inquest sitting in Brisbane on Tuesday.
"She just kept yelling and crying and talking about 'my babies are in the car' … 'why didn't I just stay in the car with them?'", Ms Ring said.
Ms Clarke was "incredibly brave" as she told Senior Constable Angus Skaines what happened with fine details like spelling names and giving dates of birth when he arrived about 8.37am.
She had sustained deep burns to 97 per cent of her body at the time, the inquest has been told.
"It was just amazing the things she was able to tell me and how much she was able to help us," Snr Const Skaines said.
Ms Clarke said Baxter told her he wanted to see his children when he got into her car.
She told him to get out but he ordered her to drive and had the jerry can in his hand.
Ms Clarke told the officer of a protection order against Baxter, and that he had tried to break her wrist two weeks prior.
The small SUV was well alight, with flames coming out every window, when firefighters first saw it as they came over a hill, station officer Anthony Eggins told the inquest.
Mr Eggins said he knew from experience anyone in the burning car had "no chance", while someone able to escape from such a fire would probably have little chance of survival.
While the car was still alight, Baxter - who sustained burns to about 80 per cent of his body - grabbed the knife from the vehicle, using it to stab himself.
Mr Eggins said firefighters attended to Baxter until more ambulance crews arrived.
He held Baxter's head steady, while another firefighter held the knife plunged into Baxter's chest and a third did CPR.
Baxter died at the scene, while Ms Clarke passed away the same day in hospital.
The inquest before coroner Jane Bentley continues.
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