Gardaí believe a dispute between different elements of the Irish biker scene led to the shooting dead of motorcycle enthusiast Andrew O’Donoghue.
There are now fears of further violence in the coming months as many bikers take to the roads around Ireland.
Three people linked to the biker scene have been arrested and were being questioned by gardaí in Limerick at Henry Street and Roxboro Road stations.
They can be held without charge for up to seven days.
The suspects were arrested last night under Section 50 of the Offences Against the State Act and are in their 20s and 40s. A number of searches have also been carried out.
Garda sources said they were working on a definite line of inquiry, with one such avenue centring on a row about two weeks ago between rival groups.
While biker gangs have been involved in the manufacture of drugs and gun related violence as well as gun feuding in other jurisdictions, the Irish scene is not marked by such serious criminality and violence.
However, there have been hostilities between different Irish groups in the past.
Mr O'Donoghue was shot outside the Road Tramps Motorcycle Club Ireland club house Murrore, Co Limerick, at approximately 3.10pm on Saturday.
A car pulled up outside the clubhouse from which a shotgun was fired in Mr O’Donoghue’s direction. The shots blasted the victim in the face, with the vehicle carrying the gunman speeding from the scene.
Mr O’Donoghue collapsed and was brought to University Hospital Limerick by ambulance. He died a short time later.
The 51-year-old dead man lived locally - at Cois na Coille, Murroe - with his partner Catherine Danaher and their daughter Ava. He had been in a relationship with Ms Danaher since both were teenagers.
Gardaí believe the dead man was the intended target of the drive-by shooting, adding it appeared those who targeted him had been watching him and appeared to have information about his movements.
The murder investigation is based at Bruff station in Co Limerick and while the row a fortnight ago between a number of men involved in the Irish biker community is now at the heart of the inquiry, Garda sources said other avenues were also being explored.
A post mortem on the dead man’s remains was due to be carried at University Hospital Limerick and was expected to concluded Mr O’Donoghue, known to his friends as ‘Odd’, died of a gunshot blast to the face.
He was closing the gate to the clubhouse at the time he was shot, with some of those from Road Tramps Motorcycle Club Ireland suggesting on social media he had called to club “to feed cats”.
The club, founded in 1987, was previously known as The Reapers. It had recently entered into an alliance with three motorcycle club chapters from Limerick, Cork and Tipperary including Road Tramps MC Ireland, Devils Disciples MC Ireland, Freewheelers MC Ireland, and Vikings MC Ireland.
A close friend of the dead man, Fr Tom Ryan, Murroe, paid an emotional tribute to Mr O'Donoghue.
“I looked upon Andrew as a good friend. I really can’t accept why this happened and why it happened to him,” Fr Ryan said, speaking Sunday morning.
“He led a peaceful life. I heard yesterday on the 6pm news. I knew Andrew very well.
“He was quiet an inoffensive man; he was a good friend of mine. He lived in the village and he had a serious interest in motorbikes.
“I’m quite shocked to hear this has happened,” he added.
The scene of the shooting was preserved by Gardai pending an examination by members of the Garda Technical Bureau.
Gardaí in Bruff have appealed for witnesses or anyone who may have any information to contact them on 062-382940, the Garda Confidential Line, on 1800 666 111, or any Garda station.
