A dead dog and a rifle have been recovered from a home in which a couple in their 70s were found dead.
South Wales Police was called to Morfa Crescent in Trowbridge, Cardiff, at about 14:50 BST on Saturday.
The force said the bodies are believed to be that of a 72-year-old woman and a 74-year-old man – although they have not been formally identified.
Police are continuing their investigations and are not seeking anyone else in connection with the deaths.
Det Ch Insp Lianne Rees said: “We understand this incident has shocked and saddened the local community.
“Extensive inquiries are being conducted to establish the circumstances leading up to the incident.
“We are awaiting the results of post-mortem examinations which will confirm the cause of death.”