Investigators are continuing to question three men in relation to the fatal shooting of Keith Walker in Clonsilla last Friday.
Gardaí in west Dublin believe the killing of Mr Walker was a case of mistaken identity.
Mr Walker (35), a father of two, was shot in the head in the yard of a pigeon club on Shelerin Road, Clonsilla about 6pm as he was delivering pigeons.
It is understood Mr Walker was due to get married later this year.
Witnesses said the gunman was dressed in women’s clothing when he walked towards the men and opened fire using an automatic weapon.
A second man also suffered gunshot wounds to his arm during the attack.
He was brought to Connolly Hospital in Blanchardstown.
Gardaí arrested two men, aged 36 and 38, in Dublin on Saturday evening.
A spokesman confirmed they could remain in custody up to seven days under the provisions of section 50 of the Offences Against the State Act 1939.
A third man, aged 32, was arrested in Co Meath on Saturday morning.
The men are being held at Finglas and Blanchardstown Garda stations.
A number of homes have been searched during the investigation.
Investigators are working on the theory that a man in his 30s from the west Dublin area was the intended target.
It is believed, however, the intended target was not present when the shooting took place.
It is understood he has spent time abroad lately and he is not in Ireland.
The intended target was one of a number of men questioned about the murder in May 2013 of a Lithuanian man.
Gintaras Zelvys had been heavily involved in organised crime in his home country before coming to Ireland and establishing himself as a businessman who ran second-hand clothes collection runs from homes throughout Dublin and surrounding counties.
The clothing was collected for charity but was exported for sale in the poorer nations.
He was gunned down on May 1st, 2013, as he and his wife opened their business outlet on the Greenogue industrial estate, Rathcoole, Co Dublin.
The intended target of Friday night’s attack had also been subjected to a punishment beating by the Real IRA in north Dublin before its leader Alan Ryan(32), was shot dead in Clongriffin, north Dublin, in September 2012.