In an outspoken attack on the killers, Archbishop Diarmuid Martin said they are "not idols or stars or heroes", but criminals who threaten public order and democracy.
Ireland's police and justice chiefs are holding talks today amid fears more death threats are circulating in a gangland feud which has claimed three lives.
The latest victim was Eddie Hutch, a middle-aged man shot a number of times last night in his home in Dublin's north inner city in an apparent retaliation for a fatal gun attack at the Regency Hotel last Friday.
The dead man was a brother of Gerry Hutch, nicknamed The Monk, who made a settlement worth millions with authorities over the proceeds of crime and money laundering in the late 1990s.
Those men are the uncles of Gary Hutch, who was believed to be the first victim in the bloody feud which stretches from Dublin's inner city to the villas and clubs of Spain's Costa del Sol.
The 33-year-old was gunned down almost five months ago at the Angel de Miraflores apartment complex in Mijas, with reports at the time saying that his killer chased him around a pool before murdering him.
Archbishop Martin called on "mothers and grandmothers" of those involved to appeal to their humanity and urge them to step back from the feared spiral of violence.
"Now we are witnessing a further escalation of violence and brutal retaliation spurred on by people whom I believe to be despicable and cynical exploiters who feel they can treat life lightly," he said.
"Is there anyone - even among their own ranks - who can speak to these cynical hearts?
"Are there some persons of wisdom - especially mothers and grandmothers who must fear that their children will be dragged even more deeply into this spiral - who see the madness of such violence and who can appeal to whatever humanity remains in the hearts of those involved?
"Every victim is some mother's son and someone's loved one and is tragically mourned by a family."
The archbishop was speaking after the shooting dead of Eddie Hutch in Dublin's north inner city in an apparent retaliation for a fatal gun attack at the Regency Hotel last Friday.
"The perpetrators are not idols or stars or heroes," said Archbishop Martin.
"They are criminals who threaten not just public order but democracy and the rule of law and who have no care for anything except their own criminal interests.
"All of us have to remind them they are not untouchable."
The church leader appealed to anyone with information to co-operate with the Garda.
