An American man allegedly told the family who fatally shot two Australian police officers he sent his "comfort and assurance" before they died in a gunfight with a tactical response team.
United States prosecutors have unveiled new details about the December 2022 shootings at Wieambilla, west of Brisbane, as part of their case against Arizona man Donald Day Jr.
Day allegedly wrote a comment in response to the suspects' online video in which they admitted killing police officers.
"Although I cannot be there ... the comfort and assurance I offer is that our enemies will become afraid of us," Day allegedly said.
Day last week pleaded not guilty in the US to five federal charges including interstate threats, threatening an FBI agent, illegal possession of firearms as a convicted felon and illegal possession of a sawn-off shotgun.
Constables Matthew Arnold and Rachel McCrow were shot in cold blood by Nathaniel, Gareth and Stacey Train after the officers arrived at the Wieambilla property.
Neighbour Alan Dare was also shot dead before the Trains were killed in a gunfight with specialist police later that night.
Between May 2021 and December 2022, Day is accused of repeatedly sending messages about a "Christian end-of-days ideology" known as premillennialism to the Trains.
Prosecutors had offered Day a deal that required him to plead guilty with a deadline to accept by May 17.
Arizona District Court records instead show Day instructed his lawyer to enter pleas of not guilty at an arraignment on May 16.
Prosecutor Gary Restaino said Gareth and Stacey Train had posted a YouTube video shortly after killing Constables Arnold and McCrow on December 12, 2022.
"If you don't defend yourself against these devils and demons, you're a coward ... we'll see you at home, Don. Love you," the Trains said.
Soon after the video was posted and before all three Trains were killed, Day allegedly responded that he wished he could be there.
"I tell you, family, that those bastards will regret that they ever f***ed with us ... anything that is within my range to do for you, I will not hesitate," Day allegedly said.
On December 16, Day posted videos in which he allegedly said the Trains were "martyrs" and police were demonic entities trying to take Nathaniel Train away due to "extensive corruption which affected children".
"When people in this box tell you violence isn't the answer ... then what is?" Day allegedly said.
When FBI agents arrested Day in December 2023, they allegedly found numerous firearms including three military-style rifles along with 20-litre buckets full of ammunition.
Day has felony convictions for assaulting police and a fellow prisoner, larceny and possessing stolen property in the states of Wyoming and California.
Lawyers for Day have sought to dismiss his firearms charge, arguing his constitutional right to bear arms was being infringed based on convictions recorded more than 34 years ago.
US District Court Judge John Tuchi on Monday ordered prosecutors and defence provide jury selection questions by September 25.
An inquest into the Wieambilla shootings is due to start in Brisbane on July 29.
