Williamson, who has won the Pulitzer Prize for photography twice, says the most vivid memory from this assignment was hearing the screams coming from the Rwandan side when he walked down the hill at night and stood on the bridge. "People were still getting hacked to death," he says. "The bad guys had figured out the route the Tutsis were taking to come into the Tanzanian side, so they'd ambush them and kill them."
The following photographs were taken immediately after he arrived at the Rwanda-Tanzania border, where he spent almost a week with the refugees. Twenty years later, he describes the moments he captured in these images.
(Warning: Some images in this collection may be disturbing due to their violent or graphic nature).
The Hutu militia went around killing everyone in a village. When they found this boy, they cut his Achilles heel so he could not walk or run. His father carried him and fled the village, and two days later they arrived at the camp. "His father said he carried him almost the entire way into Tanzania," Williamson says.
There was a volunteer burial crew at the camp because people were dying almost every night. When these group of men found a spot to bury the body, they dug a shallow grave and threw the bag with the body into it. When the body didn't completely fit into the grave, one of the guys popped the plastic bag with a stick to let out the air trapped inside. The stench of the dead body filled the air, and many people vomited.
In the early days, people still made crosses from sticks and dry twigs at a dead person's grave. But after the third day, you couldn't see any crosses being made because they needed the sticks and twigs to build fire because it was cold at night. After some point, even the older crosses started to disappear as people stole them to make fire.
This group of people smartly waited till dusk so they could dig graves when it was cooler. "The hillside was like Woodstock. There were people everywhere, and it looked like four football fields of mud. But it was not mud," Williamson recalls. "It was human waste from the refugees defecating outside." Every single time it rained, the water washed away all the waste, and it mixed into the lake that refugees were drinking out of.
Williamson was sleeping out in the open at the camp. One morning when he woke up, he saw this boy lying next to him. "I had a laundry bag full of dinner rolls that I had stolen from the banquet room of the hotel in Kenya, where I was staying," he says. "First thing I did when I saw the boy in the morning, I gave him a piece of biscuit. I never saw him again."
Many people who were fleeing Rwanda came into the camp with water they had collected from the river. Others used the water from the lake, seen here in the background, which was mixed with all the human waste washed away by rain.
"A man came up to me one morning and said his 2-week-old daughter had died," Williamson remembers. "His friend offered to dig a grave for the baby."
This was a mass grave. The burial group said doing individual graves was a lot of work, so they buried about 15 to 20 people here one evening. Next morning, people curiously stopped to look.
This is the Kigera River, where three bodies were floating in from the Rwandan side. Every five minutes or so, bodies would swirl around and then drop from the waterfall. Then more bodies would come in.
One of the Red Cross trucks stacked with grain bags had some food spilled underneath. These children, who had already suffered malnutrition, were picking up whatever they could find. Considering how hungry they were, these boys looked remarkably calm whenever the aid trucks arrived with food and water.