He was a big man; a pillar of church and community. He was the man you went to if you had problems with education for your children, or disputes over farmland. Mr Gacumbitsi was the man who preserved order in the crowded hills. Who kept a signed blessing from the Pope on the walls of his home. His was the face of authority. So when he appeared at the church on the first morning of the slaughter, Flora was completely taken aback.
And then the Mayor began shouting out instructions, urging the killers into action. The hundreds of terrified refugees, who had fled to the church at Nyarubuye, were surrounded. Slowly, the killers worked their way through the crowd, Mayor Gacumbitsi allowing them to break for lunch and go home in the evenings.
The task of killing was undertaken during normal working hours. But as one of the mob told me later, "It was exhausting work. Very difficult". To ensure that none of their intended victims could escape during the night, the killers slashed the tendons of their feet.
It is not clear if Mr Gacumbitsi literally steeped his own hands in the blood that flowed over the four long days of killing. But Flora clearly remembers that he ferried the killers to and from the village in his pickup truck and that he supplied the machetes and clubs which were used to hack and beat and gouge. More than anything, she remembers his voice, bellowing words of murder. It rose above the dull sounds of clubbing and hacking; above the cries of the dying and the pleas for mercy.
A month or so later, I tracked Gacumbitsi to a refugee camp in Tanzania where he had fled with thousands of other Hutu. With a victorious Tutsi army at their backs, Gacumbitsi and the others had feared retribution, so they crossed the border.
Not surprisingly, when I confronted the Mayor with evidence of his crimes, he denied all responsibility. "The Tutsis are the ones who say this. I am a Hutu. Do you think they like me?" he said.
It was without doubt the most frustrating encounter of my journalistic career. Gacumbitsi was clearly implicated in a monstrous crime against humanity, and yet he was able to smirk at the allegations, confident that he had escaped justice. Having watched the world stand by and allow the genocide to proceed, Mr Gacumbitsi had little reason to believe he would ever be called to account.
But something has changed in the four years since that encounter. To the best of my knowledge, Sylvestre Gacumbitsi is still living in a refugee camp in Tanzania. But he must do so now in a permanent state of fear. For he knows that any moment, an indictment may arrive which will result in his arrest and transfer to the war crimes tribunal at Arusha.
It is surely just a matter of time. Shocked by the failure of will which allowed nearly a million people to be slaughtered, the world is at last calling the architects of that apocalypse to account.
Were it not for the existence of the Arusha tribunal, it is likely that many of the worst butchers would escape any judicial sanction. It has already notched up a significant success with the admission by Rwanda's former Prime minister, Jean Kambanda, that the genocide was planned at the highest levels in government. Even the most sceptical of onlookers have been forced to accept that there has been real progress.
Likewise, in the former Yugoslavia, the international court has been steadily pressing on with investigations and indictments. Many of the more notorious criminals are still at large - Karadzic and Mladic to name but two - but like Mr Gacumbitsi, they must live in permanent fear of arrest.
The atrocities in Bosnia and Rwanda have given new impetus to calls for a permanent court to try war criminals. For the next three weeks, governments and NGOs will meet in Rome to try and reach agreement on the establishment of such a body.
On the face of it, the relative success of both the Yugoslav and Rwandan tribunals should make a compelling argument for the creation of a permanent international court. It is, we are told, time to end the culture of impunity that has governed in world affairs since the end of the Second World War. The relentless abuse of the rights of ordinary people must be brought to an end. This is all very well.
But up to now the UN security council - with Britain a notable exception - has insisted that investigations can only take place if authorised by the state where the abuse is alleged to have taken place, or by the council as a whole. The Americans fear any tribunal that would override national sovereignty or lead to possible "frivolous" prosecutions spurred by its enemies.
But a court that is not independent of the major powers, that cannot operate without the assent of the country it wishes to investigate, is in danger of becoming a toothless irrelevance. That is the central issue in the Rome negotiations. Imagine seeking the agreement of Milosevic for an investigation into his own role in the Kosovo campaign. Picture Boris Yeltsin giving the nod for a probe into Russian abuses in somewhere like Chechnya. Or the Chinese willingly accommodating the arrival of investigators in Tibet.
It is relatively easy to pursue the guilty when dealing with Rwanda. A new government has come to power determined to punish the genocide. But what if it had succeeded and Gacumbitsi and friends were still in power. Would they agree to be tried? Of course not.
However, such fears should not necessarily destroy the effectiveness of the court. If there is an answer, it is to be found in the role of the Chief Prosecutor. Judge Louise Arbour from Canada has shown, both in former Yugoslavia and in Rwanda, what an independent and vigorous prosecutor can achieve.
That is why the decision to launch investigations must lie with the office of the Chief Prosecutor - and that individual must be truly free and independent. It may well be that individual governments refuse to co-operate, that the investigators are refused visas or are wilfully obstructed (as was the case in Eastern Zaire).
But with a strong prosecutor who is able to name the guilty, the offending countries would at the very least pay a high price in public opinion. If we are not able to enforce justice, then it comes down to a simple question of moral force. We must shame the accused, even if we cannot jail them.
We must accept that a lot of the time, the killers and their leaders will escape justice. In a world so filled with human rights abuses, we can only expect to punish a few. But if nothing else, the knowledge that such a court exists may give butchers like Sylvestre Gacumbitsi food for thought when they stand all powerful before a crowd of terrified refugees.Reuse content