Thirty years ago this week, 14 Catholic civil rights marchers were gunned down by British soldiers in Derry city. Yesterday, in one of the largest rallies ever seen in Northern Ireland, their deaths were commemorated.
Few now argue that Bloody Sunday, as it became known, was a watershed event that pushed hundreds of young Catholic men into despairing of the political process and taking up the gun instead.
But still at issue, three decades later, is who fired first and who is to blame. Some in Derry believe the answers will point to the Cabinet table in London or the then Protestant unionist-dominated government in Belfast.
More importantly for today's peace process, the controversy raises questions on whether it will be possible for both Catholics and Protestants to reach agreement on their history as a prelude to a peaceful, shared future.
Some here are talking about the eventual establishment of a truth commission to open the confidential files of the main protagonists - pro-British loyalists, pro-Irish republicans, and the British government itself.
Under the South African model of such a commission, perpetrators of violence have publicly revealed their past acts without fear of prosecution, provided their actions were politically motivated and they were telling the whole truth.
"The idea of a truth commission is certainly gaining ground - but I somehow doubt it will ever come to pass unless there is a radical change of heart by those who fought this conflict," says Neil Jarman, deputy director of the Northern Ireland Institute for Conflict Research. "There has to be a willingness by all parties to reveal their deepest and dirtiest secrets - and by the state to open confidential files to full public gaze, and I see no sign of that happening."
Protestants here are voicing increasing resentment of an inquiry into Bloody Sunday, which began public hearings in March 2000 and could last another two years. (An initial probe shortly after the events exonerated the Army.)
And Protestants say two new films dramatizing the shootings, are overly sympathetic to the Catholic victims.
The films, the inquiry, and the thirtieth anniversary all come during a period of uneasy calm in Northern Ireland's troubled peace process, still plagued by disagreement amid demands that the IRA destroy more of its weapons.
Many Protestants believe that the IRA fired first on Bloody Sunday, and that the British soldiers were not to blame. Protestant leaders, then as now, have repeatedly said that the march was illegal and should never have taken place.
Protestants are furious at the price tag of the Bloody Sunday inquiry - it could total over $142 million - and the media attention given to the killings.
Gregory Campbell, a member of Ian Paisley's hard-line, Protestant Democratic Unionist Party, which wants Northern Ireland to remain part of the United Kingdom, decries what he sees as a "lack of equity about atrocities committed against our community." He says that while media and public attention is focused on Bloody Sunday, "there is no inquiry into other events that occurred around that time, when members of the Protestant community were murdered, allegedly involving the present Minister for Education in Northern Ireland, Martin McGuinness" (of Sinn Fein, the Catholic/nationalist party and political wing of the IRA, which wants one, united Ireland.)
Campbell wants an inquiry into McGuinness's past. Written evidence given to the inquiry, quoting an unnamed British secret agent's interview with an unnamed informer placed inside the IRA, claims that McGuinness confessed to firing the first shot on Bloody Sunday.
McGuinness hotly contests the British informer's claim. The Sinn Fein politician made history last year by breaking the IRA code of secrecy and admitting he was the IRA's second-in-command in Derry at the time of Bloody Sunday. In a written submission to the Inquiry, however, McGuinness says IRA members on Jan. 30, 1972, were given strict orders not to engage with British forces during the civil rights march. He says that all IRA weapons in the city had been secured in an arms dump - except two guns in case "defensive" action was needed.
Protestant resentment is understandable, says Don Mullan, author of "Eyewitness Bloody Sunday" - a book that uncovered so much evidence that it triggered the inquiry - and co-producer of one of the two recent films about the event. "We showed how the Irish civil rights movement was murdered on Bloody Sunday and how the tragedy handed the initiative over to the men of violence on all sides," Mullan says.
He praises the British government for ordering the inquiry. "It was, unquestionably, a courageous and historic step by [British Prime Minister] Tony Blair."
Britain's Northern Ireland secretary, John Reid, said on the day of the anniversary that it was time people moved on.
But, says Mullan: "We have to share an agreed past if we are to have an agreed future as equals in this peace process." He adds, however, that Northern Ireland may not be ready for a South Africa-style truth commission because there is not yet a political settlement satisfactory to all parties, and because "no one has emerged in Northern Ireland who has the potential for reconciliation or the calibre of Archbishop Desmond Tutu."
Mullan believes that, underneath unionist anger, lies a deeper concern about the lessons Bloody Sunday teaches about the very nature of the Northern Irish state. "The inquiry has set out the political context in which the murders took place. The shootings happened against a backdrop of internment without trial."
The inquiry also holds lessons for other groups of bereaved relatives. Michael Gallagher, whose son Aidan was killed in the August 1998 Omagh bombing, says he wants a public inquiry into police handling of bomb warnings before the explosion and into the subsequent investigation. "We want this sorted out now, while there's still a chance of bringing those responsible to justice," he says.