"We don't believe this attack was random or spontaneous," Queensland Deputy Police Commissioner Tracy Linford said.

"We do believe it was an attack directed at police," she said.

"There was significant evidence of advanced preparation and planning," she said.

The pandemic, climate change, social and global inequalities pushed them towards the ideology, deputy commissioner Linford said.

But there was "not one catalyst event" that motivated the shooters, she said.

Police are investigating the shooters' texts, social media posts, conducting 190 interviews and reading Stacey Train's diary.

"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 is absolutely no evidence at this time that there is anyone else in Australia that participated or assisted in this attack," she said.

Premillennialism is a branch of eschatology, a part of Christian theology.

Eschatology focusses on death and judgement, what happens to the soul, and ultimately what happens to the human race.

"There was a belief that Christ will return to the Earth for 1,000 days, and provide peace and prosperity," deputy commissioner Tracy Linford said in.

"But it will be preceded by an era, or a period of time of tribulation, widespread destruction and suffering," she said.

Premillennialists say there are four stages to human history: tribulation, second coming, millennium and final judgement.

In the first stage, tribulation, Christians endure trials at the hands of "the antichrist" and followers of Satan.

This stage is characterised by the faithful enduring distress, torture, death and martyrdom.

Premillennialists believe Jesus will return to end the period of tribulation, while other eschatologist believe he will return afterwards.

Predictions of Jesus' second coming include trumpets to announce his arrival on a white horse, with believers meeting him in the sky.

Once Jesus arrives, premillennialists believe the earth will enjoy 1,000 years with Jesus reigning and Satan restrained.

Before the last stage, the final judgment, which includes Satan escaping and starting a war with God and Christian followers.

Believers predict God wins this war, throwing Satan and unbelievers into the "Lake of Fire".