Three people are being questioned by detectives after a grandfather was gunned down in front of his sons.
Edward O'Connor was shot dead following a street brawl on Ballycoolin Road in Finglas, north Dublin, at around 5pm on Sunday.
The 41-year-old, from Barn Lodge in Finglas, was murdered after two groups of people involved in a long-running feud organised the roadside fight.
Two men in their 20s, and the woman, in her 30s, have been detained under Section 50 of the Criminal Justice Act.
They can be held for up to seven days.
Mr O'Connor was shot in the back as he walked away from the street fight, which had been arranged after one of his sons had part of his ear bitten off in a pub fight on Saturday night, gardai believe.
The long-running feud stems from Mr O'Connor being accused of abusing a woman several years ago when she was a minor.
Garda investigated the complaint, but t he Director of Public Prosecution (DPP) decided several months ago that there was insufficient evidence to charge him.
At least three of his sons were at the scene when Mr O'Connor, a settled member of the travelling community who deals scrap metal, was gunned down.
He was rushed to Connolly Hospital in Blanchardstown, where he was pronounced dead.
The scene of the shooting, between the Premier Business Park and Cappagh Road, was sealed off for several hours as forensic officers technically examined the area.
Detectives have appealed for anyone who was in the area and who witnessed the fight or shooting to come forward.