Queensland police say a deadly shooting in the rural community of Wieambilla was a "religiously motivated terrorist attack" and that the trio responsible were influenced by an extremist Christian belief system.
Nathaniel, Gareth and Stacey Train shot Constable Rachel McCrow, 29, Constable Matthew Arnold, 26, and neighbour Alan Dare at their property in the Western Downs on December 12.
Queensland Police Deputy Commissioner Tracy Linford said an investigation into the Train family had now concluded they were religious extremists who subscribed to "a broad Christian fundamentalist belief system known as premillennialism".
Here's what we know about the Christian ideology that an expert says is growing in momentum around the world.
What is premillennialism?
Premillennialism is the belief that after a period of extreme suffering, Jesus Christ will physically return to Earth for 1,000 years.
"In its basic interpretation, 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," Deputy Commissioner Linford said.
"They started preparing for the end of days.
"Christian extremist ideology has been linked to other attacks around the world, but this is the first time we've seen it in Australia."
Josh Roose, an associate professor of politics and expert on far-right and religious extremism at Deakin University, said the trio would have believed the world was "corrupt" and fast imploding.
"It is a Christian belief that in effect, the world is so corrupt, so evil, so beyond repair that at some point, in the near future, we're facing the implosion of the world effectively … an apocalyptic event and that Jesus will return to Earth," Dr Roose said.
"Historically, cults and apocalyptic cults and so-on have always looked to what's going on in the world around them and drawn upon that as evidence for the world ending."
How common is the belief system?
Dr Roose said there was "certainly a renewed momentum" in premillennialism fuelled by an "unprecedented culmination" of a "perfect storm of events".
"We've seen … significant economic decline over the last decade, climate change, global warming, catastrophic weather events increasing," he said.
"COVID too and this idea that the government was becoming all powerful and the notion that … government are out there seeking to … bring them under control.
"Combined with populist leaders, like Donald Trump, who really pushed this Christian textualist agenda, and now we see the emergence of Christian nationalism in the US … there is a renewed momentum for such movements."
Dr Roose said little was known about communities who subscribed to the ideology, but that they were "active online" and "pervasive in certain forums".
"They're poorly understood and really, there's not a lot known about to what extent they're present," he said.
Does premillennialism normally involve violence?
Mr Roose said there was always "potential for terrorism" across the "religious and political spectrum".
"This [belief] by no means represents Christianity, however, any extreme idea taken to its conclusion ... when you're talking about biblical or religious texts, effectively has the strong potential for violence."
He said it was important and a "good step" that police had acknowledged the attack as an "act of religiously motivated terrorism".
Why is it being classified as a terrorist attack?
Deputy Commissioner Linford said a terrorist attack is defined as "a politically motivated attack driven by religious-motivated extremism or ideologically motivated extremists, or sometimes even by a single-issue-type ideology".
"It generally will result in death or serious injury … to somebody or serious damage to property, designed to intimidate government," she said.
"It's contained within the criminal code from Commonwealth statute.
"You don't have to be part of a group."
Queensland police said they do not believe any other people locally were involved in planning the attack but they are working with the FBI in the United States as part of their investigation into people who commented on the Trains' social media posts.
