An ambush attack in a remote Australian town that left six people, including two police officers, dead was a "religiously-motivated terrorist attack", authorities said on Thursday.
Police believe it was the first act of terror linked to Christian extremist ideology in Australia.
Constables Matthew Arnold, 26, and Rachel McCrow, 29, were killed in an ambush shooting when they arrived at a property in search of a missing person in Wieambilla, located more than 300km west of Brisbane, on 12 December.
Nathaniel Train, his brother Gareth, and sister-in-law Stacey, opened fire at the officers when they approached the residence on the property. The police returned fire but two officers and neighbour, Alan Dare, died in the gunfight.
Deputy police commissioner Tracy Linford said Nathaniel, Gareth, and Stacey Train acted as an autonomous cell and executed a planned attack that was directed at the police.
"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, according to the Australian Broadcasting Corporation.
Ms Linford added that the trio saw police "as monsters and demons".
There was significant evidence of advanced preparation and planning, the officer said, adding that police found camouflaged hiding places at the property, barriers such as dirt mounds and logs, firearms, knives, bow and arrows and a trap door among others.
Ms Linford said the police investigated 190 documents, social media posts and including Stacey's extensive diary entries.
There was no evidence to suggest at this time that there was anyone else in Australia that participated in the attack.
The deputy commissioner said the Covid-19 pandemic, conflicts across the globe and social disparity contributed to their belief.
"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."
