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.