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A man has been arrested in the United States over online comments that allegedly incited violence before the "religiously motivated terrorist attack" in regional Queensland where two police officers and an innocent neighbour were slain.
Queensland Police said officers travelled to the US to meet with Federal Bureau of Investigation (FBI) agents to arrest a 58-year-old US man near Heber Overgaard in Arizona on December 1.
Constables Rachel McCrow, 29, and Matthew Arnold, 26, and innocent neighbour Alan Dare, 58, were shot dead at close range by Gareth Train, 47, Nathaniel Train, 46, and Stacey Train, 45, at the Wieambilla property on December 12 last year.
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The Trains were shot dead by heavily armed police hours later.
The series of events that allegedly linked the 58-year-old US man to the Trains began two years before the massacre.
Police allege Gareth began following the man on YouTube in May 2020.
He and the man began commenting directly on each other's videos in May 2021.
"We have evidence to show the Trains subsequently accessed an older YouTube account created by the same man in 2014 and viewed the content," Queensland Police Service Assistant Commissioner Cheryl Scanlon said.
Between May 2021 and December 2022, the man allegedly sent repeat messages containing "Christian end-of-days ideology" to Gareth and Stacey.
Scanlon confirmed the man is connected to a YouTube video posted by the Trains on the night of the confrontation.
This evidence has been seized and analysed by the FBI.
Scanlon said the Trains were motivated by a "Christian extremist ideology and subscribed to the broad Christian fundamentalist belief system known as premillennialism".
After investigations, a grand jury issued two indictments to the man, one of which relates to comments posted online in December 2022 inciting violence over the Wieambilla attack.
The other indictment is not connected to the Wieambilla attack, Scanlon said.
The man faced court today and was remanded in custody in the US.
A search warrant has also been carried out at a remote property in northern Arizona in relation to the incident.
Investigations are continuing.
Scanlon said the FBI is investigating the man over alleged offences committed in the US jurisdiction and he will face the US courts for those alleged crimes.
However, she did not rule out the man facing charges in Australia.
"It is early days, this matter is before the coroner – there is an ongoing investigation," she said.
Scanlon said the Wieambilla attack involved advanced planning and preparation against law enforcement.
She called it a "religiously motivated terrorist attack".
Arnold, McCrow and Dare's family have been briefed on the progress of the investigation, police said.
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A formal inquest into the massacre will occur in mid-2024 to investigate the deaths and possible ways to prevent a similar incident in the future.
The inquest will include looking into the online activities of the Trains and "identify possible associates who may have influenced them in their actions".
It will also consider how NSW Police communicated with their Queensland counterparts when requesting they attend the Wieambilla property.
