Jason Ryan was stabbed several times and later died when his attacker called at his front door in Hollyville Heights in Wexford in the early hours of yesterday.
Gardaí believe the 27-year-old, originally from Ferndale in the town but living in the quiet estate with his partner, fell out on to the street after being knifed.
It is believed the altercation between the two men continued outside the house as Mr Ryan tried to fight off his attacker.
Senior detectives said they are following a definite line of inquiry.
It is understood Mr Ryan had been in a relationship with his attacker’s ex-girlfriend.
The suspect was released early from a five-year jail sentence for an assault in Wexford in 2007 in which a man was left in a coma.
It is understood that Mr Ryan, who had a number of convictions, had been living in rented accommodation in Hollyville with his girlfriend.
A Garda spokesman said he suffered several stab wounds and was taken to Wexford General Hospital after his partner called the ambulance.
He died as a result of his injuries several hours later.
A spokesman confirmed that several crime scenes have been identified.
Mr Ryan’s home has been sealed off for forensic examinations and the Garda Technical Bureau and staff from the state pathologist’s office were also called in.
A house in the nearby Talbot Green area has been sealed off and a car is also being inspected as part of the investigation.
Detectives appealed for anyone with information to contact officers in Wexford.
Meanwhile, three men were questioned last night about the murder of Limerick man Ger McMahon, who died in a knife attack last week.
Mr McMahon, 43, of Raheen Square, Ballinacurra Weston, was found with stab wounds lying outside a house at Lenihan Avenue, Prospect, at 12.35am on January 18.
An autopsy found he had been stabbed at least eight times in the upper body.
Two men in their 20s were arrested yesterday in the Limerick area. They were both detained under Section 4 of the Criminal Justice Act at Roxboro Road and Mayorstone Garda Stations.
A man aged in his 30s arrested on Tuesday, also in the Limerick area, and was being held under Section 30 of the Offences Against the State Act at Bruff Garda Station.
They bring to six the number arrested in relation to the killing.