Detectives investigating the murder of a Dubliner shot dead in the city on Tuesday evening believe his killing was not connected to gang or drug activity, but related to a personal grudge.
Fine Gael said the killing was the latest in a series of attacks in which "ordinary people" were being increasingly targeted by armed gangland criminals.
Raymond Collins (42), Matt Talbot Court in Dublin's north inner city, was shot dead by a pillion passenger on a motorbike at about 5pm as he walked down Clonliffe Avenue close to his home.
Within hours of the murder, two men who were known to the victim were arrested for questioning. They are both in their 20s and are from the north inner city.
Gardaí believe the two men were involved in an assault on Mr Collins last month in a pub, which left him badly injured. They believe the men may have decided to target the father of five again in this week's fatal gun attack.
The motorbike that gardaí believe was used in Tuesday's murder has been found at Clarence Street flats, close to the murder scene.
A number of searches of nearby properties were also carried out late on Tuesday when clothing was taken away for examination.
The dead man had a number of convictions for public order offences, burglary and assault. He was not involved in organised crime but had a reputation as a heavy drinker who regularly became involved in serious pub brawls. He almost lost his life in one such incident about six years ago after he was stabbed in the stomach.
The two men under arrest last night were being questioned under Section 30 of the Offences Against the State Act. They were being held at Fitzgibbon Street and Mountjoy Garda stations and can be held without charge until tomorrow evening.
Fine Gael's spokesman on justice said he was "horrified" that Mr Collins had apparently lost his life at the hands of those who decided to settle a personal grudge with a firearm.
"Under Michael McDowell's watch, we have reached a situation where criminals can mete out their own twisted and evil form of justice as they see fit," he said.
"Ordinary people are increasingly being targeted by gangland, with organised criminals routinely launching tiger kidnappings against bank staff, supermarket assistants and post mistresses."
Labour Party TD Joe Costello, in whose Dublin Central constituency the murder took place, said gangland crime had been allowed to thrive under the current Government. "Gardaí must be given the resources to allow for a sustained campaign to put these killers behind bars. If this does not happen, the terrible murder toll will continue."
"We have seen the emergence of a new breed of vicious criminals, who have easy access to deadly weapons and are prepared to use them."
Despite some successes on the part of the Garda, such as Operation Anvil, "the battle against the gun gangs" was not being won.
"The fact that a murdering gang has claimed yet another victim . . . is further evidence of the virtual impunity with which these dangerous thugs believe they can operate," Mr Costello said.