Gardaí investigating the murder of a man in Bray discovered the body of a second man during their examination of the garden of the house where the killing took place.
They say they are not looking for anyone else in relation to either death.
Det Insp Frank Keenaghan described the incident as very tragic for three families.
The first victim, who lived at the house on Cuala Grove, has been named as 22-year-old Sebastian Creane.
The second dead man, who was also 22, has not yet been named. The two men were not related.
Mr Creane's brother is currently being treated for wounds inflicted on him by the attacker in St Vincent's University Hospital.
A woman, who was also injured by a single stab wound, is undergoing surgery at another hospital and is expected to make a full recovery.
The bodies of both the deceased young men were taken from the house by hearse this afternoon.
Gardaí say they are still trying to piece together what happened in the house. But they believe the man who drove Sebastian Creane and another friend back to the house, attacked Sebastian, who then sought the help of his brother who was in bed.
The attacker then turned the weapon on Sebastian's brother, and another woman who was in the house.
They say they will not speculate about the cause of death of the unnamed man in the back garden, but say they are not seeking anyone in relation to either death.
The Creane brother's parents, who were out of the country, are now back in the area.