A man is being questioned by police after a million dollar reward was announced to help solve two linked cold-case homicides.
NSW Police raided a property in Murwillumbah in the state's north on Tuesday as part of their investigation into the 2002 deaths of Iain Stewart Hogg and Frederick Rosson.
Acting Inspector Chris Elliott said a 56-year-old man was being questioned about the murders.
"I can't disclose any more than that as it is part of the investigation," he told reporters on Tuesday.
Investigators believe Mr Hogg was shot and dumped in the Tweed River in northern NSW in 2002, however his body has never been found.
The 45-year-old's red Toyota Celica was seen in a car park in the area on March 11 that year and witnesses said they saw a group of people before there was a flash and a loud bang.
An appeal has been made directly to the LGBTQI community for anyone who knew Mr Hogg.
"We believe that Mr. Hogg was part of that community back in 2002," Inspector Adam Bennett from Queensland Police said.
"He was very private person, so we're really appealing to that community who may feel more safe and obliged to come forward now in relation to any information they have."
Three days after Mr Hogg's murder, 67-year-old Frederick Rosson, who also went by Charles "Slim" Johnson, was shot dead at his property in Mt Nathan, Queensland.
Police believe he was killed by two gunmen who went there to look at a 9mm CZ handgun he had advertised for sale, that was subsequently stolen.
Mr Hogg's Celica, which police suspect was stolen after his murder, was seen in the vicinity of the property and found dumped at Palm Beach on the Gold Coast the following week.
A joint reward, comprising $500,000 each from the Queensland and NSW governments, was announced earlier on Tuesday for information leading to an arrest and conviction in the murders.
Acting Insp Elliott said investigators believed the same people were responsible for both killings.
"We are confident the car used to access Mr Rosson's home was Mr Hogg's Toyota Celica and we believe the same men were involved in each incident," he said.
"To those in the community who know what happened to Mr Rosson and Mr Hogg, it's time for you to come forward."
More than 150 witness statements have been taken and 600 inquiries conducted by police all over Australia.
NSW Police Minister Yasmin Catley said investigators had never given up on finding answers for the dead men's loved-ones.
"Our hope is that this reward will encourage people to come forward with anything suspicious or untoward they might have heard or seen at the time," she said.
Inspector Bennett from Gold Coast police said investigators hoped the $1 million would lead to a breakthrough.
"It is never too late to come forward," he said.
"Relationships and loyalties change, people who were once scared may no longer be and we would encourage these persons to come forward."
