The gun used in an apparent murder-suicide in northwest Tasmania that left two men dead and a woman injured had been circulating unregistered in the community for 25 years.
Police say Paul Carey, 35, shot 32-year-old Chris Walters at a house in Devonport in the early hours of Saturday before turning the gun on himself.
A woman who was also shot at the address remains in hospital in a stable condition. A 10-year-old boy and baby were in the home at the time.
Tasmania Police has previously said Carey acquired the Winchester shotgun in the past three months.
Inspector Kim Steven said the weapon had not been handed in or registered when stricter gun laws were implemented nationally after the Port Arthur massacre in Tasmania in 1996.
"(The gun) has been circulating in the community until this incident," Insp Steven said in a statement on Tuesday.
Officers are speaking to a 30-year-old man, who has been described as an associate of Carey, about the gun.
"I urge anyone in the community who has an unregistered or unwanted firearms to contact police," Insp Steven said.
"People can surrender firearms at any time under a permanent amnesty, without fear of being prosecuted for the possession."
Police say all three people in the shooting are connected and jealousy may have been a motive.
Mr Walters has been remembered by friends as a "kind soul" and someone who would help out when needed.
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