In the grisly chronicle of the war in Lebanon, no horror can rival last month's massacre of Palestinian refugees in Beirut. After a summer-long siege by Israeli troops and the forced evacuation of 11,000 PLO fighters, the city had grown calm. Then, on Tuesday, September 14, it was rocked again by the assassination of Lebanon's President-elect Bashir Gemayel. Israeli forces immediately occupied West Beirut, surrounding the two adjacent Palestinian refugee camps of Shatila and Sabra. The next day the Israeli forces allowed Christian Phalangists and Lebanese militia to enter the camps that were home to nearly 20,000 Palestinians. Before the Phalangists and militia left 40 hours later, more than 500 men, women and children lay dead in the streets and in hastily bulldozed graves. Tineka Ulug, a 30-year-old Dutch nurse, and 19 foreign medical workers who were stationed at the Gaza Hospital inside the Sabra camp, lived through the three-day reign of terror. Afterward Ulug recounted those terrible hours for PEOPLE's Beirut correspondent Mary Davis Suro

I was asleep on my balcony in my apartment near the camps on Wednesday, September 15, when at 5 a.m. I was awakened by two Israeli jets flying low overhead. This was the first time since the end of the summer war that I had heard that sound, and it was terrifying. When I left for the hospital at 7 a.m., I saw many people loading up cars as if they were leaving. The Israelis had returned to West Beirut, and the people who were fleeing felt certain, I think, that this could only mean additional torment for them.

All day and up until Thursday evening there was continuous shelling and shooting in the camps. I assumed that the fighting was a result of an Israeli roundup of remaining Palestinian fighters in Beirut. It wasn't until Thursday that I began to think there could be something more going on. Early that afternoon frightened people started coming to the hospital saying that they heard Phalangists were in the camps, which measured approximately one mile by a half mile. But after a summer of war, these people were still frightened and easily excitable, so we really didn't listen. By evening hundreds of people had gathered at the hospital seeking protection. There were people in the wards, people on the stairs and even people sitting in front of the hospital. There was a general panic, and old women sat crying and shaking their heads in fear. Since then I've wondered how I could not have realized something was going on. I simply didn't.

Thursday evening I went back to my apartment. That night was strange and disturbing. Starting at about 7 p.m. until early the next morning, flares lit up the camps like a football stadium. The next morning, Friday, I returned to the ward at 7 a.m., and it was still overrun by people. But gradually they started leaving. Looking back, I think they must have had an idea of what was happening in the camps and realized that even a hospital could not protect them.

On Friday afternoon the International Red Cross sent word to the hospital that roaming soldiers had entered Akka Hospital just south of the camps. They had allowed the foreigners to leave but had killed two Palestinian patients and two Palestinian doctors. They had also raped a Palestinian nurse, 22-year-old Intisar Ismail, a friend of mine, and then shot her. At this news we decided that the Palestinian doctors and nurses must leave. The rest of us, however, chose to stay and keep the hospital functioning. Two Palestinian nurses insisted on remaining with us as well.

Again on Friday evening, the hospital was mobbed by civilians looking for a haven and also a great number of men and boys who were presumably fighters. We now realized what a risk it would be to have them under our roof, and we forced them to leave. Many had come totally unarmed and were completely terrified. It was an awful thing to have to do.

All 22 of the medics stayed at the hospital Friday night. I slept very little because we were 10 to a room and we felt unnerved. I remember others remarking how deathly quiet it was outside. We wondered what was going to happen.

On Saturday morning at 7 a.m. a soldier arrived and ordered us out of the hospital but allowed two doctors to remain with the patients too sick to move. There were eight more soldiers waiting for us. At first we thought they were Israelis because they were dressed smartly in combat gear. We soon realized they weren't. The soldiers told us we were to be taken to headquarters about a mile away, but that we would be brought back. We were told to walk three abreast, and when we arrived at the main road, we suddenly saw hundreds of men, women and children sitting by the side of the street. Many tried to walk in line with us, but soldiers roughly pushed them away. There was terror in those people's faces. The two Palestinian male nurses were with us, and I recall feeling relieved that the soldiers had let them come. It was not long afterward, though, that both were pulled out of line. I could not look back, so I did not see them shot, but I knew then for certain that was their fate.

As we moved south on the main road through the camps, we began to come upon dead bodies. They were not only lying in the streets but were heaped like rubbish into crowded alleyways. What horrified me most was the tangled configuration the bodies took. It was horrible. The first two bodies I saw were two very old men in their pajamas, with bullet holes in their heads. Next we came upon a group of women and children, and I think this was the worst. I saw one woman who, even in death, clung to her child. As we came to the south exit of the camps I thought I could take no more. It was then I saw two bulldozers scooping up dead bodies from the streets.

When we were well out of the camps, two trucks rounded a corner and started driving toward us. Sixty soldiers walked alongside them. Someone next to me said this must be the firing squad to execute us, and it seemed certain because at that point we were adjacent to a brick wall. But the trucks and soldiers passed us by.

In the courtyard of the headquarters our identification papers were taken, and the soldiers launched into a fervent speech about the respect they held for the Geneva Convention. The next thing we knew an ambulance was driven into the courtyard, and the soldiers pulled out a Palestinian boy about 15 years old. He had been shot in the chest, and they paraded him in front of us, showing his wound and asking us to notice how well they had treated him.

After individual interrogations, we were turned over to the Israelis who were headquartered directly across the street. From there we were put on trucks and taken to the American Embassy. While we were with the Israelis, we were not asked a single question as to what we had seen in the camps or what had transpired there. I'm amazed at this now.

During the summer war I didn't know a single person who was killed. Now I could give you a list of 30 people, all murdered. Most of them worked in hospitals as cooks, cleaning women, doctors, and now they're all dead. This experience was a thousand times worse for me than the war. There was death and destruction then, but in a war there is usually a reason. With this, it is too horrible to comprehend. This, not the war, will give me nightmares the rest of my life.

The body of one Palestinian nurse was later found in the rubble of Shatila. The other is still missing. Thirteen members of Gaza Hospital's foreign staff have since left Beirut, but Ulug and four others remained to work with the surviving refugees.