“They had to break into the floor and found three bodies,” he said. The couple’s daughter, who the grandfather called Abnysh , had just turned five in September.

“How do you do this? Kill your own child?” he said.

Mr. Schlecht said his daughter had married Mr. Tedl a about seven years ago. They met at Columbia University, where she studied public health and social work. He added that his daughter was a giving person who often traveled to Kenya and other African countries to help the needy.

Ms. Schlecht worked for the United Nations Foundation in New York, officials said. According to her LinkedIn page, she was a senior adviser specializing in reproductive health, humanitarian response and other issues.

Her co-workers said that after years of helping women and girls in Africa get access to health care, she continued her efforts out of the foundation’s New York office to spend more time with her daughter.

“She delighted in telling us about her daughter’s first day of kindergarten and the clothes she picked out all by herself,” said Beth Schlachter, an executive with the foundation. “That she should die under such brutal circumstances is beyond our understanding. But we will all remember her for her life — and the thousands of lives she enriched — rather than the horrible way she died.”

Mr. Tedla worked as a computer contractor at Columbia University Mailman School of Public Health, in the population and family health department.

When the Schlecht family first met Mr. Tedla, who is originally from Ethiopia, he seemed like a “very smart, clever person,” Mr. Schlecht said. But later, he added, Mr. Tedla became violent toward Ms. Schlecht and she tried for years to leave him. He refused to go, ripping up the divorce papers each time.