A 54-year-old Italian national was stabbed to death by a juvenile following an apparent domestic dispute, gardai believe.
The victim, named locally as Bruno Rolandi, was discovered with a number of serious knife wounds at a house on Sunday night.
It is suspected that he suffered at least two stab wounds at the home he shared with his partner in the Ballyfore area of Edenderry, Co Offaly.
Last night, detectives were continuing to question a 17-year-old male in relation to the father-of-two's death.
Gardai are probing if the suspect acted in self-defence during a domestic dispute at the home.
In total, four people are understood to have been in the property at the time of the killing, including the victim and the arrested youth.
Mr Rolandi is originally from the Monza region of Italy but had been living in Edenderry for some time.
Investigating officers were yesterday informing his relatives in Italy of the tragedy.
A garda spokesman said emergency services were alerted to the incident at 7.48pm, and discovered the victim with knife wounds.
"Despite the efforts of medical personnel, the man in his 50s was pronounced dead at the scene," the spokesman said.
"A juvenile male was arrested in relation to the incident and is currently detained under Section 4 of the Criminal Justice Act, 1984, at Tullamore Garda Station."
Gardai are currently not looking for anyone else in relation to the incident.
An incident room has been established at Tullamore Garda Station, from where the probe is being co-ordinated.
Locals yesterday expressed shock after news of the killing emerged.
"Everyone is in total shock. The family would be well known in the area," said Independent councillor Noel Cribbin.
"It is a very quiet area. It is a real tragedy."