The Queensland police officers fatally shot while making a welfare call at a Western Downs property last week also had plans to arrest one of the gunmen.
Constables Rachel McCrow and Matthew Arnold, and neighbour Alan Dare, were ambushed and killed by Nathaniel, Gareth and Stacey Train at the Wieambilla residence, three hours west of Brisbane, on December 12.
The Trains were all later shot dead in a gunfight with police reinforcements.
Four constables initially went to the property to check on Nathaniel Train after he was reported missing by his wife but also planned to take the former school principal into custody.
Deputy Police Commissioner Tracey Lindford said on Thursday Nathaniel Train was wanted on an outstanding warrant for damaging a border gate while entering the state from NSW and dumping two unregistered guns near a creek on December 17, 2021.
"The reason they were going there was because of the warrant and the events of December last year, and the missing person report," she told reporters.
Local officers had been trying to call the Trains about the warrant and had gone to the property to arrest the younger of the brothers multiple times over the past year but no one was ever home.
"I don't know the exact number but it was multiple visits by local police to try and talk to or try and locate Nathaniel Train in the first instance, but to talk to him about the incident back in December, and they were unable to locate him," Ms Lindford said.
The deputy commissioner said local officers had never found any red flags about the Trains, who weren't on any police watch lists either.
Despite the apparent lack of danger, last Monday's house call ended shockingly differently for police than all their earlier visits.
"This was a run-of-the-mill policing job," Ms Lindford said.
"Our police attend addresses every day of the week and execute warrants on individuals, and given the fact we had very little history or knowledge about or any concerning behaviour about Nathaniel Train, there wasn't anything to flag particular concern with our members who were attending the scene that day."
Detectives are still working out the Trains' motive after ruling out domestic terrorism and are probing their social media posts and bank accounts.
"What we can see is sentiment displayed by the three individuals, or three Train family members, that appears anti-government, anti-police, conspiracy theorist type things," Ms Lindford said.
"But we can't see them connected to any particular group they might have been working with or inspiring them to do anything. We haven't had anything like that at this point in time."
Police have also seized six guns - two registered to Nathaniel Train, three unregistered and one of unclear ownership - as well as compound bows, arrows and knives from the property.
Those details come a day after thousands of people bid an emotional farewell to Constables McCrow and Arnold at a memorial where Police Chaplain Jeffrey Baills urged people to remain stoic in their grief.
"We have had a major attack on the police in Queensland but, ladies and gentlemen, I want to say to us today, 'we will not be broken'," he said.
The two officers were awarded valour medals at the ceremony at the Brisbane Entertainment Centre.
Police Commissioner Katarina Carroll has posthumously awarded the bravery medal to Mr Dare, who will be farewelled at a private funeral in Ipswich on Friday.
