The bodies of the 77-year-old woman and the 46-year-old man were located by police at an Albany Creek residence on Sunday afternoon.
The man's 88-year-old mother was also home at the time but was unharmed.
All three lived at the Jambaroo Street property, police said.
"This is a tragedy, there is no doubt about that," Detective Acting Superintendent Craig Williams said on Monday.
Emergency services were called to the residence in Brisbane's north after reports of a shooting about 5.30pm on Sunday, police said.
The pair were known to each other according to initial police investigations. (Darren England/AAP PHOTOS)
Det Supt Williams said the man fired a number of shots from his registered handgun at his aunt before using the firearm on himself.Â
Police had been called to the home several times and "had dealings with both parties" in the days preceding the shooting.
But Det Supt Williams would not elaborate on why when he addressed the media on Monday.
"As the matter is still under investigation, it would be inappropriate for me to comment on exactly what happened during those hours," he said.
There was no history of domestic violence, he said.
The man's mother was assisting police with their investigation, police said.
"This is a tragic incident and we are assisting the family to the best of our ability," Det Supt Williams said.
"The matter is still under investigation, it only occurred yesterday and we're conducting inquiries with the family and all witnesses."
Anyone with information should contact police.
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