The attack happened at around 5:30am today, Sunday, in a six-bed general ward at the hospital.
Matthew Healy was a retired farmer from Berrings in County Cork and is survived by his daughter, two sons and eight grandchildren.
Gardaí have arrested a 32 year old man in relation to the investigation and are questioning him at the Bridewell Garda Station.
Gardaí believe the victim did not know his alleged attacker.
Garda Press say a post mortem examination was carried out at Cork University Hospital by Assistant State Pathologist Dr Margaret Bolster. The details of the post mortem are not being released for operational reasons.
A Senior Investigating Officer has been appointed and a Garda Family Liaison Officer continues to liaise with Matthew Healy’s family.
The scene at the Mercy University Hospital remains preserved for a forensic and technical examination by the Cork City Divisional Scenes of Crime Unit.
In a statement to RedFM News, the Mercy University Hospital said they are providing counselling services to patients and staff affected by the incident.
They also said they are “saddened and shocked at the tragic and unexpected death” of a patient.
Management also expressed their “deepest condolences” to the family, relatives, and friends of the deceased.
