NSW police have said the Wieambilla shooting that killed two police officers and an innocent neighbour was a "religiously-motivated terrorist attack" motivated by an extremist Christian belief known as premillennialism. 

Emeritus Professor in the History of Religious Thought at The University of Queensland Philip Almond told Gary Adshead premillennialism believers hold the view that there will be a time of tribulation, where the Christians who are left behind on Earth will need to be ready to defend themselves. 

"To them within that worldview, the arrival of the police was the arrival of the antichrist, they're the force of evil," Professor Almond said.