PHOENIX — The FBI has arrested an Arizona man in connection to a fatal attack on police last year in Australia for what prosecutors say were threats made against law enforcement and the head of the World Health Organization.

On Friday, agents arrested 58-year-old Donald Day of Heber-Overgaard in Navajo County, Arizona, on two counts of interstate threats, according to a statement from the U.S. Attorney's Office. Day was remanded into custody after he appeared in court on Tuesday, court records show.

The first count stems from a video that prosecutors say Day posted on YouTube on Dec. 16, 2022, days after what Australian police have called a "religiously motived terrorist attack" that left six dead, including the three attackers.

In the video, Day referenced the ambush and subsequent standoff and threatened to injure law enforcement officials who came to his residence, according to an indictment filed Nov. 29. Day's YouTube username was "Geronimo's Bones," the indictment said.

"The devils come for us, they ... die. It's just that simple," Day said in the video, according to the indictment.

The second count is connected to a comment prosecutors say Day left in February on a video posted on the video-sharing site BitChute. According to the indictment, the video showed the WHO director-general, Tedros Adhanom Ghebreyesus, and included Day saying, "It is time to kill these monsters, and any who serve them. Where are my kind? Where are you? Am I the only one?"

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Prosecutors: Day showed 'desire to incite violence'

From about the beginning of 2022 until Feb. 2 this year, Day demonstrated a "desire to incite violence" and threatened a variety of groups and individuals including law enforcement and government authorities, according to the indictment.

Nathaniel Train and Stacey Train, who referred to themselves as "Daniel" and "Jane" on YouTube, commented back and forth with Day on videos they uploaded. On Dec. 12, 2022, in Queensland, Australia, the couple and Nathaniel Train's brother, Gareth Train, killed state police officers Rachel McCrow and Matthew Arnold, and bystander Alan Dare.

Police had been investigating a missing person report when the attack occurred. Two officers managed to escape and called for help, which resulted in a six-hour standoff and the eventual killing of the three preparators.

How is Donald Day's case connected to the Australian terrorist attack?

After the murders but before their deaths, Nathaniel Train and Stacey Train posted a video on YouTube called "Don't Be Afraid," where they said, "They came to kill us, and we killed them," according to the indictment.

They also said, "We'll see you when we get home. We'll see you at home, Don. Love you," the indictment said. 

Day commented on the video, "Truly, from my core, I so wish that I could be with you to do what I do best," according to the indictment. He then made at least two other videos supporting "Daniel" and "Jane," according to the indictment.

"Our brother Daniel and our sister Jane were harassed on a regular basis by authorities ... in the province of Queensland to hand over his brother to them because his brother was on the verge of revealing the extensive corruption which affected children," Day said in a video, according to the indictment. 

Day's trial has been set for Feb. 6 in the federal courthouse in Phoenix. He faces a potential five-year prison sentence if convicted.

Contributing: The Associated Press