Something seismic is happening in Limerick at three o'clock this afternoon. A father observing the month's mind for his murdered son will lead a people's march to city hall to stop the killings. Even those with the best will in the world doubt it will make any difference. On blogs since the rally was announced the battle-weary have been dismissing it as futile.

Their mistake is that they under-estimate Stephen Collins. The criminal who ordered the murder of his son made exactly the same mistake.

The killers must know they picked on the wrong man when they shot Roy Collins dead on Holy Thursday because someone he was related to had refused to serve alcohol to a criminal's under-age sister in a bar. Two nights after burying his son, Stephen Collins wept on RTÉ's Prime Time. That was the first seismic moment in this defining phase for Limerick.

His grief immersed sitting rooms throughout the country. He was bereft. He recalled Roy, as a little fellow, imitating him, wanting to be like his dad. On Holy Thursday, someone had run in to Stephen's pub and yelled that there had been a shooting. He found Roy on the floor of his gaming arcade, frightened of dying. As the life ebbed out of him, he told his father he loved him and he asked him to tell his mother he loved her too.

It was compelling television. What raised it to the high tidemark for Limerick's gangland crime was when Miriam O'Callaghan asked, were he able to rewind time, would he do anything different. No, he said, because you have to do what's right. If the criminals who terrorise Limerick have any intelligence, they will have felt footsteps on their graves as he uttered those words.

It was a moment reminiscent of Colin Parry's seminal grief when his 12-year-old son, Tim, died in the IRA bombing of Warrington while buying a Mother's Day card in 1993. Tim's death, and the death of Johnathan Ball, aged three, were the defining tragedies that redirected Northern Ireland on to the road to peace. There had been ceasefires before and popular peace movements warranting Nobel prizes, but what made Warrington different was that, in Colin Parry, it produced an individual with an outstanding capacity for reconciliation who became a channel for change. Eighteen months after the bomb, the IRA's history-changing ceasefire came into force.

Stephen Collins is another extraordinary father. He has organised today's march because, he says, he does not want his son to have died in vain. A fortnight after burying Roy, Stephen and another of his sons were threatened with death in broad daylight on a public street. The man's courage in withstanding such intimidation is encouraging, but so too is gangland's disquiet at the force for good that he has come to represent. If Roy succeeded in his endeavours to emulate his father, his murder is an even greater loss than we first appreciated.

Every time someone is murdered in Limerick, demands ensue for stiffer sentences and harsher punishments, but the most effective response is a community's unambiguous rejection of the murderers. After Veronica Guerin's death, the country turned on the criminals, forcing the political establishment to react substantively. Such was the heat, criminals turned on each other.

On Friday night, a bunch of politicians bleated on The Late Late Show that they wanted to reform our system of government but it was too formidable a task to take on.

In Limerick, a grieving father with no electoral power was getting ready to rescue his city from the abyss. Some day, maybe, the politicians will name a bridge in Limerick after Stephen Collins.

jmccarthy@truibune.ie