A man has been arrested by the FBI over a domestic terrorist attack that led to the shooting deaths of two Queensland police officers.

Constables Matthew Arnold and Rachel McCrow were gunned down in cold blood by Nathaniel, Gareth and Stacey Train after the officers arrived at their Wieambilla property, west of Brisbane, in December 2022.

Constables Randall Kirk and Keely Brough escaped the attack but neighbour Alan Dare was also shot dead after going to check on the property.

The Train brothers and Stacey, who was Gareth’s wife, died in a subsequent gunfight with specialist police.

Investigators later said the ambush was a domestic terror crime motivated by extremist Christian beliefs.

On Wednesday, Queensland said a 58-year-old US national had been arrested last week in Tucson in Arizona in connection to the deadly ambush.

“On November 29, at Arizona, two indictments were issued by a grand jury for interstate threats … One of the threats made relates to comments posted online in December 2022 inciting violence in connection to the incident at Wieambilla,” Queensland Police Assistant Commissioner Cheryl Scanlon said.

“On Friday, 1 December, 2023, US time, FBI agents arrested a 58-year-old man in Arizona. Earlier today, at 2pm US time, the 58-year-old appeared in court and has now been remanded in custody.”

Scanlon said a search warrant had also been executed at a remote Arizona property as police and the FBI continued their investigations.

“We know the offenders executed a religiously motivated terrorist attack in Queensland,” she said.

“They were motivated by a Christian extremist ideology and subscribed to the broad Christian fundamentalist belief system known as premillennialism. The motivation of the United States national is still under investigation by the FBI.”

Believers in premillennialism subscribe to the idea that, after a period of extreme suffering, Jesus Christ will return to the Earth in the second coming and reign for a millennium.

“We know that Gareth Train began following the 58-year-old man on the online platform YouTube around May 2020. Gareth and the man began commenting directly on each other’s videos in May, 2021,” Scanlon said.

“We have evidence to show the Trains subsequently accessed an older YouTube account created by the same man in 2014 and viewed the content. Between May 2021 and December 2022, the man repeatedly sent messages containing Christian end-of-days ideology to Gareth and
then later to Stacey.”

Last week’s arrest came after Queensland Police investigators travelled to the US to join the FBI and other law enforcement officers.

The FBI’s legal attache in Canberra, Nitiana Mann, said the organisation understood that last year’s attack still resonated across Australia.

“The FBI has a long memory and even longer reach – from Queensland, Australia, to the remote corners of Arizona,” she said.

“The FBI and the QPS worked jointly and endlessly to bring this man to justice and he will face the crimes he is alleged to have perpetrated.”

Scanlon said police had worked through “every single line of inquiry” of anyone who had contact with the Trains.

“To date, there is nobody else connected in Australia that we have been able to uncover,” she said.

The man arrested in Arizona was a contact of the family who was detected during the police investigation.

Earlier police said the Queensland coroner and the families of Dare and the dead officers, as well as other officers involved in the Wieambilla incident, had been briefed on the latest developments.

-with AAP