Three people who killed two Queensland police officers and a neighbour in December last year executed a "religiously motivated terrorist attack", police say.
Deputy Police Commissioner Tracy Linford said Nathaniel, Gareth, and Stacey Train acted as an autonomous cell and executed a planned "attack directed at police" at Wieambilla in December.
They shot Constable Rachel McCrow, 29, Constable Matthew Arnold, 26, and neighbour Alan Dare at their property in the Western Downs on December 12.
"We don't believe this attack was random or spontaneous," Deputy Police Commissioner Linford said.
"We do believe it was an attack directed at police.
"There was significant evidence of advanced preparation and planning."
Police found camouflaged hiding places at the property, barriers such as dirt mounds and logs, six firearms, three bow and arrows, a number of knives, CCTV, radios, mirrors on trees, and a trap door under the house, which might have enabled an easy escape.
Deputy Commissioner Linford said police had been investigating Stacey Train's diary, as well as the trio's texts, social media postings and 190 interviews.
"What we've been able to glean from that information is that the Train family members subscribe to what we would call a broad Christian fundamentalist belief system, known as premillennialism," she said.
Deputy Police Commissioner Linford said the trio saw police "as monsters and demons".
She said the COVID pandemic, climate change, global conflicts and social disparity contributed to their belief in their system.
"Whilst the behaviour was similar in some respect to sovereign citizens, we don't believe this was connected to a sovereign citizen ideology, we believe it's connected to the Christian extremist ideology," she said.
"There was a belief that Christ will return to the Earth ... and provide peace and prosperity.
"But it will be preceded by an era, or a period of time of tribulation, widespread destruction and suffering.
"They started preparing for the end of days."
'Not one catalyst' for extremism
Deputy Commissioner Linford said police had garnered from Stacey's diary, which was written over the last few years, that there was "not one catalyst event" which led to their extremism, but Nathaniel's heart attack in 2021 made him more religious.
Other factors included Nathaniel and Stacey losing their jobs — as a principal in Walgett primary school in NSW and head of curriculum at a school in Tara in Queensland — because they did not get the COVID vaccine.
"They certainly had their views around anti vaccination, and as a consequence of that, anti-government," she said.
Deputy Commissioner Linford said police do not believe any other people were locally involved in planning the attack.
"There is absolutely no evidence at this time that there is anyone else in Australia that participated or assisted in this attack," she said.
However, police are working with the FBI in the United States over people who commented on the Trains' social media posts.
She said Christian extremist ideology has been linked to other attacks in the world, such as the Waco massacre in the 1990s, but this was the first time it had occurred in Australia.
She said the coroner will make the final determinations on the motivation and what led to the attack.
No 'ringleader' among them
The four officers went to the property to follow up an outstanding warrant relating to firearms and a border breach by shooter Nathaniel Train, as well as a missing person report.
Nathaniel was reported missing by his wife in NSW and after crossing the border during COVID restrictions, he went to the Wieambilla property owned by Gareth and Stacey.
An officer visited the address in August last year and later tried calling the Trains.
"I don't think there's any question that they would have known that at some point in time police were coming, but whether or not they would have anticipated it was specifically that day, we wouldn't say that," Deputy Commissioner Linford said.
"The way that they had set their property up, there are clear indications that they had done a lot of planning."
She said police did not know Nathaniel was residing at the address at the time of the siege, but thought he could have camped in bush nearby.
Deputy Commissioner Linford said police would have anticipated that Nathaniel had three firearms with him, but he didn't have any previous serious criminal history.
"There was nothing to indicate to the members that would have attended on that day, that they were going to be ambushed," she said.
Deputy Commissioner Linford said there was no indication from Stacey's diaries that she was a victim of domestic violence and "she clearly had a view similar to what we saw from Nathaniel and Gareth".
Furthermore, there was no particular "ringleader" among them, she said.
"When you have three acting together, it's challenging to say it's a mental health issue," Deputy Commissioner Linford said.
Police have taken statements from the family of the trio.
