Detectives believe an ex-soldier turned bomb mule was beaten to death over a local dispute.
Larry Keane, 56, was found lying in a huge pool of blood on a walkway near a housing estate in Athy, Co Kildare, at about midnight on Thursday.
The one-time Irish soldier had served time in jail for trying to smuggle an explosive twice the size of the Omagh bomb into the UK in 1998.
But despite his links to dissident republicans, gardai said his killing had none of the hallmarks of a paramilitary assassination. Instead, they are focusing on rows the father of six had with others in the small town in recent months.
"He was living on his reputation," said one source. "He used to be considered a heavy, but he wasn't in good health and didn't have the physique to back it up anymore."
Keane was found semi-conscious after suffering a severe blow to the back of his head. Detectives believe he may have been kicked to death or struck with a blunt instrument.
Keane, who lived near the scene of his murder and was well known around the town where he was regularly seen walking with a stick, was taken to Naas Hospital where he died in the early hours of Friday morning.
The alarm was raised when local officers were called shortly before midnight with a report of a man lying in the walkway between St John's Lane and Greenhills. He was thought to be returning to his home in Canal Close when he was set upon.
Keane, who had children to a number of partners and was living with his son, was a soldier between 1974 and 1980. During his trial for a major explosives offence in 1998, he said he was recruited while in Portlaoise Prison for assault and agreed to move the bomb "for a few bob".
He was jailed for 15 years after gardai stopped him in a BMW car packed with explosives and queued for the ferry in Dun Laoghaire two days before the Aintree Grand National. The 980lb bomb was twice the size of the device planted in Omagh a few months later.