“Alternatively, it may have been left in or near a hut or rural structure,” he said.
The bodies of Brendon and Trina Cole were discovered on December 13 and a homicide investigation was launched.
Bouterey said “significant work is ongoing” in relation to the investigation and he thanked people who provided statements or supported the investigation.
“The co-operation shown by the community has been invaluable and we acknowledge the effort it takes to come forward in what remains a difficult and distressing matter,” he said.
“We know individuals who hold information that could assist the investigation have not yet spoken to police, and the information you hold could help provide answers to two families who are grieving.
“To those people, we urge you to reconsider and contact us.”
Bouterey said there was no information to suggest any risk to the public.
Anyone who has found a firearm near the relevant areas or has knowledge of where it may be should contact police immediately and not touch it.
“Even information that may seem minor or insignificant could be critical in progressing this inquiry.”
Anyone with knowledge of firearms that belonged to the occupants of 470 Murumuru Rd is also asked to contact police.
Information can be provided through 105, either online or over the phone, referencing file number 251213/6207 or Operation Murumuru.
Alternatively, information can be provided anonymously through Crime Stoppers on 0800 555 111.