Local sources have suggested the victim was recently acquitted of abuse allegations.
A man is being questioned about the discovery of a body in Mayo.
He was arrested on suspicion of murder following a house fire in Castlebar yesterday.
The victim has been named locally as 83 year old John Brogan.
Emergency services were called to the scene of a fire at a house on Pheasanthill in Castlebar shortly after 6.30 yesterday evening.
Mr. Brogan's body was discovered inside the house - with reports he had suffered a number of gunshot wounds.
Local sources have suggested Mr. Brogan was recently acquitted of abuse allegations.
Gardaí have since arrested a man on suspicion of murder, who's being questioned at Castlebar Garda Station - and the services of the State Pathologist have been requested.
Anyone with any information in relation to the case is urged to contact any garda station or the Garda Confidential Line.

€1.2m Approved For Zipline And High Ropes Adventure Centre At Donadea
Christmas Appeal To Adopt Dogs As Euthanasia Figures Rise
Speed Enforcement To Increase In Kildare With 21 New Camera Zones To Be Rolled Out In January
Over 400 Motorists Caught Speeding So Far Today, Including A Driver In Kilcock
Transport Minister In Discussions With Irish Rail About Extending Late-Night Trains Beyond Christmas
Tadhg And Mary Should Be Looking Forward To Christmas, Say Gardai As Fresh Appeal Launched
Bus Shelters Treated As Luxury Rather Than Standard, With 500 Kildare Bus Stops In Need Of Upgrades
Recruitment Announcements Don’t Add Up As Garda Numbers Stagnant In Kildare South, Says Local TD