Leo Fransen's crew from Diamond Beach, on the mid-north coast, was on its first day of a three-day deployment to fight the 21,370ha fire when he was struck on Thursday.
NSW Rural Fire Service commissioner Rob Rogers said the falling tree hit the brigade leader "very, very hard" and he died, despite the first-aid efforts of other volunteers and paramedics.
Mr Fransen was a 13-year veteran of his local brigade who had recently been made captain and he leaves behind a wife, two children and a large extended family.
"This obviously is a significant impact to not only his family but to the RFS itself," Mr Rogers said on Friday.
"It is a tight, family-type unit, the RFS, and these things are incredibly difficult for everybody involved and we will obviously be continuing to support (his family) as best we can."
Yesterday afternoon, Captain Leo Fransen was tragically struck by a tree whilst fighting the Hudson Fire in the Walgett LGA. After receiving initial treatment and being transported to the Lightning Ridge health facility, Captain Fransen unfortunately passed away. — NSW RFS (@NSWRFS) pic.twitter.com/J5bh6vIvTYNovember 16, 2023
The Hudson Fire at Glengarry, near Walgett in northwestern NSW, has been burning since Sunday, when the RFS believes it was sparked by a lightning strike.
Since then it has destroyed six buildings and on Wednesday it triggered an emergency warning, although by Thursday night it was being brought under control.
Emergency Services Minister Jihad Dib said Mr Fransen's tragic death was a reminder of the dangers that firefighters exposed themselves to during what was likely to be a "very difficult" bushfire season.
"The 70,000 volunteers that give up their time to protect our communities are absolutely heroic and this is the worst news that you can imagine that reverberates through the organisation at this time," he said.
The fatal incident follows the October death of an RFS volunteer who died after experiencing a medical episode on a fireground in the Kyogle region, in the state's northeast.
Total fire bans are in place for two regions in northern NSW on Friday, including the area surrounding Walgett but the risk is expected to ease over the weekend.