Police recovered the bodies of an elderly couple from their home in Sadar upazila of Sherpur on Tuesday afternoon.
The deceased were identified as Md Shamsul Haque, 85, a resident of Fakirganj village in the upazila and his wife Sayera Begum, 78.
Family members said they found the couple dead in their room this morning and informed the police.
Later, police recovered the bodies and sent these to Sherpur Sadar Hospital morgue for autopsy this afternoon.
The deceased's son Md Rafiqul Islam claimed his father was mentally imbalanced and would often beat up his mother.
Sadar Police Station officer in-charge Basir Ahmed Badal said poison smell was found on Shamsul's mouth and blood stain on Sayera's ear.
Police primarily assume that the elderly man might have committed suicide by taking poison after killing his wife, he said.
The process is underway to file an unnatural death case in this connection, the OC added.
Imran Hasan Rabbi/SU