He has been named locally as Matt ‘Matha’ Shirley from the Wakehurst Road area of Harryville.
Initially, police said that the death of the 69-year-old in the Drumtara area of Ballymena yesterday afternoon was being treated as suspicious.
However, following a post mortem examination MIT detectives set up a major incident room after the death was confirmed as murder.
Two men, aged 41 and 49 and a 47 year old woman arrested yesterday as part of the investigation remain in police custody.
They are being questioned at the PACE suite at Antrim police station.
The suspects can initially be held for 24 hours before being either released or charged.
Detectives can apply to a judge for an extension to their detention in custody.
Detective Chief Inspector Alan Dickson is continuing to appeal for information.
He is is keen to speak to anyone who was in the Drumtara area from Sunday evening until teatime yesterday and who has any information about an altercation involving a group of people to contact the MIT detectives on the non-emergency number 101.
Alternatively information can be passed anonymously via the independent charity Crimestoppers on 0800 555 111.