Qld shooting link to conspiracy forums

The brothers allegedly behind a shooting ambush at a remote Queensland property in which two police were killed had gone off-grid and become linked to online conspiracy theory networks before the deadly attack.

Nathaniel and Gareth Train died in a gunfight with heavily armed police at their Wieambilla property in the Western Downs on Monday night.

The pair, along with Nathaniel's wife Stacey, allegedly ambushed and shot dead constables Matthew Arnold, 26, and Rachel McCrow, 29, and their 58-year-old neighbour Alan Dare before the trio was killed.

NSW Police last week launched a public appeal to find Nathaniel Train, 46, a former schoolteacher who was last seen at his Dubbo home on December 16, 2021.

He had cut contact with his family in early October and was reported missing on December 4 this year.

Police on Wednesday said his family held serious concerns for his welfare.

Queensland Police Commissioner Katarina Carroll said NSW police had asked local officers to check on the 46-year-old, who was believed to be at his older brother's Wieambilla property.

"That person had been missing for up to about 12 months, but people had been in contact with him," she told reporters.

"However, that contact was lost in recent days and they just wanted to check on that missing person."

Nathaniel Train worked as executive principal at Walgett Community College Primary School, but the NSW Education Department said he hadn't been employed in the state's education system since August 2021 and he officially left employment in March.

While at the school in northern NSW, he sent 16 emails over two weeks about problems there and the need for assistance, state parliament heard in May.

Sources told AAP that Nathaniel Train had been living off the grid after leaving his teaching position before heading to his 47-year-old brother's home in Queensland.

A series of posts under the name of Gareth Train appear on conspiracy theory forums and include references to anti-vaccine sentiments and claims high-profile shootings were hoaxes or false-flag operations.

One post refers to "black op police'' and urges people to prepare themselves.

"Has reading anything from the 1901 constitution or quoting common law to the black op police with the guns helped anyone in Victoria and their rights," a post from a user named Gareth Train said.

Local media reports indicate Gareth and Stacey Train owned the property where the ambush occurred.