She was not shy about speaking out.

Brian Palmer, a friend who had invited her to speak to his class at Uppsala University, where he teaches, described her as an exuberant person who candidly spoke about the United Nations’ limitations.

“She was not at all shy to talk about difficult questions,” he said. “She had come to see the people that she was trying to help as her equals and her friends and had very much loyalty to them.”

The two, accompanied by an interpreter and drivers, all Congolese, had gone to a part of Kasai-Central Province in early March to investigate the fighting there, which pitted the Congolese Army against an array of rebel factions.

They traveled by motorcycle, the only way to navigate the area. Going with United Nations peacekeepers would not have been a good idea because they are not always trusted by gunmen.

“They were doing what we’ve all done,” said Jason Stearns, a former member of the Group of Experts who now runs the Congo Research Group at New York University. “Getting a couple of motorcycle guys, getting an interpreter. And they trekked out to rebel territory, which Michael has done so many times, hundreds of times probably.”

The experts are not everyone’s friends. They uncover inconvenient facts about people committing crimes, and higher-ups helping them. In their previous reports, the experts had implicated some military officials in wrongdoing. The part of Kasai-Central Province they had traveled to had lately been littered with suspected mass graves, and the Congolese Army was blamed for some of them.

Image Zaida Catalan, from Sweden, was known for candidly speaking about the United Nations’ limitations.

There were reports of children being conscripted to fight. Ms. Catalan was responsible for investigating child soldiers, among other things. Mr. Sharp was the coordinator of the panel.