GardaÍ are investigating whether a 35-year-old man who was stabbed to death by a 25-year-old was killed as part of "a row or a psychotic episode" in the capital's latest murder.
Both men had been living in a HSE-run psychiatric facility on St Lawrence Road in Clontarf.
Gardaí said the victim, who was named locally last night as Michael Olohan, was not known for involvement in crime, nor was the suspect, who handed himself in only minutes after the fatal attack.
The attack happened at the support facility at about 7.15am yesterday.
Sources said Mr Olohan died from stab wounds to the chest after a "disagreement" between the two men, who were known to one another.
The suspect was gone from the scene when the emergency services and gardaí arrived.
However, within minutes he presented at Clontarf garda station, where he told officers he had stabbed a man.
The suspect was arrested, but it is understood he was transferred to hospital as he had wounds to his hands.
Gardaí are examining whether mental health issues were behind the stabbing.
"Gardaí are not looking for anyone else in relation to this tragic death," a source said.
The scene was sealed off by gardaí as the investigation got under way.
Members of the Garda Technical Bureau arrived just before 11am to begin a forensic examination of the area.
The property where the stabbing happened is an HSE-run psychiatric facility, according to local councillor Nial Ring, who said it is a long-established centre that is well integrated with the local community.
"It's a very well-run place and is never a source of trouble, so the whole community are shocked," Mr Ring said.
Gardaí were concentrating their investigation in an outdoor passageway that runs down beside the facility that fronts on to St Lawrence Road, and connects it to another building behind.
The facility is a low-support, independent living residence for mental health rehabilitation.
In a statement, an HSE spokeswoman said: "The HSE can confirm that there was a fatality in an incident this morning that occurred in a low-support residence in North Dublin.
"Families are being notified and residents have been moved to alternative accommodation."
Gardaí are appealing for anyone with information in relation to the incident to contact them at Clontarf garda station on 01 666 4800 or the Garda Confidential Line on 1800 666 111.