The 47-year-old has been charged with more than 30 historical sex offences after being arrested at Brisbane airport.
Police said the man assaulted six women and children known to him in north Queensland between 1998 and 2023.
"It will be further alleged on some occasions the man committed the offences while armed with a firearm," police said.
Police released images of bullets after the man's arrest at Brisbane airport. (HANDOUT/QUEENSLAND POLICE SERVICE)
Police released a video of the man's arrest at Brisbane airport last week along with photos of a rifle and bullets.
A day after the man's arrest, a crime scene was set up at a north Queensland cattle station where an unregistered firearm and ammunition was recovered.
Police allege the man assaulted women and children known to him in Charters Towers, Cloncurry, Hughenden, Normanton, Richmond and Winton.
Detective Acting Senior Sergeant Forbes Malseed said police had identified multiple witnesses across Australia and Europe during their investigation.
"This has been a protracted investigation and we believe there are more people across the globe who can provide information to assist us," he said.
Police allege the man had a rifle when he is accused of sexually assaulting some of his victims. (HANDOUT/QUEENSLAND POLICE SERVICE)
"These victims have shown immense bravery in coming forward and we will continue to protect vulnerable young people.
"We are urging anyone who may be a victim to come forward and speak to us and assure them all offending will be investigated fully."
The man was charged with a string of sex offences including 17 counts of indecent treatment of a child and seven counts of rape.
His matter was adjourned until August 12 after he appeared in Brisbane Magistrates Court and was refused bail last week.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
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