The Swiss official, speaking on condition of anonymity, said that he had recognised up to 30 militiamen whom he knew had massacred civilians.
He told of people herded into compounds across southern Rwanda, doors being closed and grenades being thrown in. He said he had seen many such instances in the 10 days that it had taken him to flee Rwanda.
The medical aid worker said: 'I would lose my job if I identified them. Under the Geneva Convention I am not allowed to. But there is one man who I would shoot the balls off and leave lying in the sun. He is here. Forgiveness is hard.' Refugees have repeatedly told aid workers in Benaco camp that militiamen and their leaders fled with them and were moving about in gangs, often trying to steal food handed out by aid groups.
The killing of President Juvenal Habyarimana in a rocket attack on his plane on 6 April set off massacres, blamed largely on his army and loyalist militiamen, both dominated by his Hutu tribe. Victims have been mainly the minority Tutsi or Hutus suspected of opposition to Habyarimana's government.
The Red Cross official said there should be a United Nations war crimes tribunal and he would be willing to testify if his masters in Geneva would sanction it. He said: 'I was trying to evacuate one seriously wounded woman in my car. The militia let down my tyres, rigged the battery and, grenade and panga in hand, calmly told me she must die there. I have washed the car inside three times. But if I leave it in the sun for half an hour, the smell will simply not go away.' The chilling conversation took place under clear skies in some of the world's most beautiful tropical country.
Walking through this now well-established city in the light of day, it is difficult not to look at the men and wonder if this individual or that may be one of the killers.
'In almost every case when they were killing they would leave some people alive,' the Red Cross official said, adding: 'A militia commander told his men: 'We cannot exterminate them all, we must leave some to give a historical record of what we have done'.' The Red Cross says there are at least 90,000 people in 10 camps displaced in south-east Rwanda. The largest holds 40,000. But the killers have fled into Tanzania.
There are both Hutus and Tutsis in the Benaco camp, latest estimates show there are now almost 200,000 people. The mass influx has stopped but people are still coming in.
The people here are immensely resourceful. Grass huts have sprung up among the plastic given by aid agencies. From the young to the old, they have taken what they need for shelter from the surrounding country. The camp is taking on the air of a permanent city.
In any big city there are unknown killers and criminals. But in this, Africa's newest city, the killers are known. Camp leaders have told residents not to speak to reporters about the killers. The refugees know it would be unwise to do so.
Leading article, page 19