Thomas Grams, 51, gave up his dental practice in Durango, Colo., to provide free care to Afghan and Nepalese kids.
Brian Carderelli of Harrisonburg, Va., has been identified as the sixth American killed.
British doctor Karen Woo, 36, called herself an "explorer kitten." A former dancer and model, Woo gave up a job as surgeon to deliver aid to Afghanistan's most needy. Last year she fell in love, and was supposed to be married in just two weeks.
"I'll miss her love for life probably the most," said Woo's finance, Mark Smith. "The fact that anybody who met her couldn't help, but smile. The fact that she made people happy. She helped people."
Thirty-five year old Daniela Beyer of Chemnitz, Germany, was a translator.
Bodies of the victims arrived Sunday in Kabul, where many will be buried. The Americans' bodies will be flown back to the U.S. for an autopsy.
Markus said in his conversations with Little, he did not discuss the dangers of the mission, but said it's "part of living and working in Afghanistan."
"It's an undercurrent that's there and you just accept it and acknowledge it, but don't dwell on it. It was one of the most admirable qualities about [Tom Little] and the others in the group that I got to meet," he said. "They had work to do, they were there to help the people, and that was really what they focused on."
The Associated Press contributed to the report.