Former Walgett Primary School principal, Nathaniel Train has been confirmed to have shot and killed two young Queensland police officers on December 12 at around 4:30 pm at his family's property in Wieambilla.

Mr Train was later shot dead by police along with his brother Gareth Train, and Gareth's wife Stacey who owned the property.

Mr Train had been reported missing to the Central North Police District on Sunday, December 4 by family and friends after they could not get in contact with him.

He was last seen in the NSW town of Dubbo on December 16 2021 and was in contact with family members until October 9, 2022.

Four police officers had arrived at Gareth Train's property in Wieambilla, four hours north-west of Brisbane to conduct a welfare check as part of the missing person case.

The officers arrived at the scene and walked up the driveway to speak to the occupants of the property, before being ambushed by bullets.

Two constables, confirmed as Matthew Arnold, 29, and Rachel McCrow, 26, were confirmed dead at the scene, shot in "execution style" as well as 58- year- old neighbour Alan Dare who travelled to the property to investigate the scene.

PHOTO: Nathaniel Train, ex-principal of Walgett Primary School has been confirmed as having been involved in the shooting at Darling Downs in Queensland. (Source: NZ Herald)

Queensland Police Union President Ian Leavers says the two officers "had no chance" at survival.

"This ruthless, murderous trio have gone and executed the two police officers on the ground in cold blood," Mr Leavers said.

"We have never seen anything like this. It is an absolute tragedy. This was pure execution... they had no chance," he said.

Sixteen police officers were then called to the emergency and attempted to save the lives of their colleagues.

"They wanted to do what they could to save their lives," Mr Lavers said.

"Sadly, they did this under heavy gunfire, and nothing could be done to save their lives. A member of the public went to investigate and he was shot in the back. That is an absolute tragedy as well," he said.

Nathaniel Train is former principal of both Walgett Primary School and Yorkeys Knob State School in Queensland.

Heartfelt tributes and condolences have been circulating around Australia to the families of the murdered officers just two weeks out of Christmas.

A crime scene has been set up and an investigation is underway, which is predicted to take a number of weeks or even months. A coronial inquest will also be held.