Experienced firefighters say they have never seen anything like the fire tornado in the Upper Murray which led to a truck rolling over and a volunteer losing his life.
A coronial inquiry is investigating the 2019 and 2020 fires, including the blaze which started in the Woomargama national park on December 29 and burnt for 53 days.
Firefighter Samuel McPaul died about 5.45pm on December 30 when a fire tornado formed and rolled his Culcairn fire truck onto its roof.
He died of traumatic asphyxia.
The coroners court on Tuesday heard there was no suggestion of driver error.
Investigators believe two lightning strikes about 4.30pm on December 29 sparked the blaze in the south-east corner of the national park, in extremely steep rugged terrain.
It burnt in a south-easterly direction, with the terrain hampering initial efforts to contain the fire which had first been spotted by nearby residents.
Mr McPaul was with two others the following day at a property called Lightwood on River Road at Jingellic.
One firefighter from the Lankeys Creek brigade said as conditions deteriorated, "I could see the fire getting bigger and bigger and I could tell we were in for a s---fight".
Another firefighter, Captain John Hawkins, said the fire jumped containment lines and got away in the early afternoon of December 30 as conditions deteriorated.
Bureau of Meteorology experts believe the fire tornado which developed was consistent with a category three tornado, which involves winds of 220km/h to 260km/h, and may have reached category four levels up to 320km/h.
"As I looked up the hill I could see a large whirlwind or tornado starting to build up," Captain Hawkins said in a statement.
"It was a large column of black smoke swirling in a clockwise direction and throwing burning lots of sticks and leaves out into the surrounding paddock.
"I hadn't seen anything like this tornado before, I have seen small fire whirlies but nothing like this one."
He guessed it had been several kilometres high and several kilometres wide.
Volunteer Jason McBain said "there was fire coming from all angles".
He feared being overrun, but it changed direction immediately and travelled away from him.
"I have never seen this occur before," he said.
Nearby resident Scott Anderson said the blaze changed dramatically in a minute and sucked wind into it, causing a fire truck to vibrate.
The fire was building energy inside itself moments before it became a "huge, swirling mass".
Ashley Drummond said spot fires were sucked into the main fire and began to "twist and turn into what I could only describe as a fire tornado".
Several conditions, including pyrocumulus clouds, moderate winds above the surface and the location of the blaze created favourable conditions for a fire vortex.
The 10-tonne Isuzu crew cab fire truck rolled about 5.45pm.
Driver Andrew Godde and passenger Rodney O'Keeffe were injured but survived the rollover.
Mr O'Keeffe suffered serious burns and was airlifted to hospital and Mr Godde was treated for burns to his hands.
The pair will give evidence on Wednesday with a RFS captain and policeman to also be called.
Adam Casselden, counsel assisting the inquest, stressed that driver error had been ruled out in the rollover.
"There is absolutely no evidence that would suggest there was driver error," he said.
The inquest heard foul play had been ruled out as the cause of the fire and investigators had located the origin.
Albury Detective Sergeant Dane Kremers said items like lighters, cans, cigarette butts and tyre marks which could suggest arson were not found at the scene.
The fire destroyed 14 homes in Ournie, Talmalmo and Jingellic.
Detective Acting Inspector Hassan El-Khansa said the fire travelled 25 kilometres on December 30 and 45 kilometres the following day.
"To travel 70 kilometres in a two-day period is a significant movement of fire," he said.
"It's not what we consider normal fire progression."
Tuesday's evidence focused on the cause of the fire.
Mr Casselden will make submissions into the cause and origin when the matter returns on Wednesday.
An inquest into Mr McPaul's death will then begin.
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