Three shooters rigged a sophisticated surveillance system to help them "take police out" at a remote Queensland property where they ambushed officers, killing two constables and a neighbour, the police union says.
Forensic examinations are continuing where Constables Matthew Arnold and Rachel McCrow and neighbour Alan Dare were gunned down on a Wieambilla property on the Western Downs, 300km west of Brisbane, on Monday.
Queensland Police Union president Ian Leavers says there's evidence the killers Gareth Train, his wife Stacey, and brother Nathaniel, who were all shot dead, planned the attack and set up a camera system.
"It was a sophisticated surveillance system and that is very, very concerning to us, knowing that this ruthless, murderous trio went to this extent with a view to I firmly believe, to take police out," he told ABC Radio on Thursday.
"As other investigations are continuing, I'd like to be able to say more, but I can't because I'm very cognisant of the investigation, I don't want to hamper it, but we are very, very concerned, and it s sickening to know the lengths that this murderous trio went to."
Police are also looking into the Train brothers' online activities, including their possible involvement in extremist conspiracy groups and forums.
Online posts in the name of Gareth Train featured a mix of conspiracy material, including claims that high-profile shootings were hoaxes or false-flag operations.
Mr Leavers said the dual police and union investigations could take another week to work out what happened to Constables Arnold, 26, and McCrow, 29, and Mr Dare, 58, and why.
Constable Keely Brough, 28, who escaped the ambush by hiding in long grass, which the shooters then ignited, is taking time off with her family, he said.
Her colleague Constable Randall Kirk, who also got away, is recovering at home with his pregnant wife and daughter after having surgery to remove shrapnel f rom his leg.
Mr Leavers said Constable Kirk may need further operations, but both officers are doing as well as they can.
"We are so very fortunate that Randall and Keely are still with us as well, it was close," he added.
Queensland Police Commissioner Katarina Carroll has met with the families of Constables Arnold and McCrow and said she has learnt a lot about the two officers.
"We learnt a lot about what they did as children, why they wanted to become police officers and...their friends and family backgrounds," she said on Thursday.
"The families are amazing people who had children who wanted to do great things in life."
Ms Carroll has also been in touch with officers Brough and Kirk.
"They are resilient, amazing young officers that knew exactly what to do," she said.
"They're well, they're grateful they're alive, but they're incredibly saddened that during that same incident they lost two of their colleagues."
Details about a memorial service for the fallen officers are expected in coming days.
Prime Minister Anthony Albanese, who previously said the officers paid a price no one who puts on the uniform should ever pay, will lead tributes to the pair in federal parliament on Thursday.
The Train brothers' father Ronald Train said he was struggling to comprehend how his sons, who cut ties with him 23 years ago, could be responsible for the killings.
"I just could not understand how something like this could have occurred, with two children who had been raised by my late wife Gwen and myself," the retired pastor told Nine's A Current Affair on Wednesday.
"They went down this track, this dark track, which we have no understanding of."
Ronald Train officiated at the wedding of Nathaniel and Stacey some years ago, adding he was surprised by reports the older brother, Gareth, was now married to the same woman.
Australian Associated Press