More charges may be laid after a US citizen was linked to a religiously motivated terrorist attack in Australia that left two police officers and a good Samaritan dead.
Donald Day Jr, 58, was arrested by the FBI in Arizona after a US federal grand jury indicted him on two counts of "interstate threats" following the December 2022 fatal shootings in Queensland.
The first indictment is connected to what was described as Australia's first domestic terror attack motivated by Christian extremist ideology.
Constables Matthew Arnold and Rachel McCrow were gunned down in cold blood by Nathaniel, Gareth and Stacey Train after the officers arrived at a Wieambilla property west of Brisbane on December 12 last year.
Neighbour Alan Dare was also shot dead before the Trains were later killed in a gunfight with specialist police.
A joint Queensland Police-FBI investigation is ongoing, with evidence seized from a remote property near Heber-Overgaard, Arizona after Day was arrested last week.
The second indictment against Day relates to an alleged online threat to kill the World Health Organisation director general in February.
Each count carries a maximum US jail term of five years.
Queensland Police Commissioner Katarina Carroll was hopeful more charges would be laid in the future.
"People need to be held to account for inciting that," she said of the 2022 attack on Thursday.
"That is deplorable behaviour, particularly what he was inciting people for - motivating against police, against authorities - which is completely unacceptable."
The indictment connected to the shootings relates to a December 2022 YouTube video Day allegedly posted days after the Wieambilla attack.
"Day posted a video on YouTube threatening any law enforcement official who came to his residence," a US Attorney's Office of Arizona statement said.
In an unsealed indictment, it is alleged Day posted the YouTube video on December 16 2022 under the name Geronimo's Bones, referring to Gareth and Stacey Train as "Daniel and Jane".
"My brave brother and sister, a son and a daughter of the Most High have done exactly what they were supposed to do, and that is to kill these f***ing devils," Day allegedly said in the video.
He is accused of later saying: "Like my brother Daniel, like my sister Jane, it is no different for us.
"The devils come for us, they f***ing die. It's just that simple."
Day allegedly threatened to kill the head of WHO and calling on others to join him earlier this year on video platform BitChute under the username WEAREALLDEADASF***, describing himself as "an x-con who's armed to the teeth".
It is alleged Gareth Train began following Day's YouTube account from May 2020.
The men began commenting on each other's videos a year later, police said.
Between May 2021 and December 2022, Day is accused of repeatedly sending messages containing "Christian end-of-days ideology" to the Trains.
The Trains subscribed to a broad Christian fundamentalist belief system known as premillennialism.
Gareth and Stacey Train uploaded a video on a now-deleted YouTube account hours after the fatal shootings, referring to police as "devils and demons" and sending love to someone called Don.
Day allegedly wrote in response: "I so wish that I could be with you to do what I do best.
"I tell you, family, that those bastards will regret that they ever f***ed with us."
Day is in custody after appearing in a US court this week.
The US Attorney's Office of Arizona said it was handling the prosecution.
Ms Carroll said she was incredibly proud of investigators and their "relentlessness in pursuing this".
"Because people need to be held to account," she said.
"That tragedy happened nearly 12 months ago... a tragedy that I don't think the organisation will really ever truly recover from."
