As she headed to Mali a week ago, Anita Datar was in high spirits. She told her friends on Facebook that she had not visited West Africa since leaving Senegal in 1999. Back then, she was a Peace Corps volunteer. Now she was a 41-year-old global health policy expert for an international development firm.

“Love that I’m in Mali!” she later said in an e-mail to a friend, Amy Kay, in the District. “So happy.”

Her joyful message came just two days before gunmen stormed the Radisson Blu Hotel in Bamako, where she was staying with two co-workers. Her colleagues made it out unharmed. She did not, becoming the only American killed in a siege Friday that left at least 21 people dead.

That day, Leanne Dougherty left work early after hearing about the attack and huddled with ­Datar’s parents, who were caring for her 7-year-old son at her home in Takoma Park, Md. Dougherty found Datar talented, exuberant and effortlessly glamorous, even in the most trying circumstances.

“I was waiting for her to walk out of the hotel with big glasses, and her hair done and heels,” said Dougherty, who had hired Datar at Palladium, the international development company she worked for in Washington.

Anita Datar of Takoma Park, Md., was the only American killed when gunmen seized the Radisson Blu Hotel in Bamako, Mali. At least 21 people where killed in the attack. (WUSA9)

Instead, she and Datar’s parents waited hours for word. At 2:30 p.m. they learned that Datar was listed as missing. “It was excruciating,” Dougherty said.

Two hours later, the U.S. ambassador to Mali called Datar’s parents to confirm her death.

As word spread among friends and colleagues, Datar’s death touched off a wave of mourning that on Saturday reached from colleagues in Washington and neighbors in Maryland to the front-runner for the Democratic presidential nomination.

“The world is a darker place without your light,” one stunned friend wrote on Datar’s Facebook page Saturday. “I am praying for your little boy.”

Her family issued a statement Friday voicing similar devastation.

“It’s unbelievable to us that she has been killed in this senseless act of violence and terrorism,” her brother Sanjeev Datar said in the statement. “Anita was one of the kindest and most generous people we know. She loved her family and her work tremendously. Everything she did in her life she did to help others — as a mother, public health expert, daughter, sister and friend.”

The Washington Post's Kevin Sieff talks about the extremist threat in West Africa and why the U.N. peace keeping mission there is now the agency's most dangerous. (Kevin Sieff and Jason Aldag/The Washington Post)

Her brother said that while the family is saddened and angry about Datar’s death, “we know that she would want to promote education and health care to prevent violence and poverty at home and abroad, not intolerance.”

The divorced mother of a ­second-grader, Datar was Palladium’s senior director for field programs for Health Policy Plus, a project funded by the U.S. Agency for International Development aimed at improving reproductive health in developing countries. Datar had devoted much of the past 10 years of her career pursuing global public health, particularly family planning and HIV prevention and response.

Edward Abel, president of Palladium’s U.S. business unit, said that he did not have details about what unfolded inside the hotel or how Datar was killed while her colleagues escaped. “From what I understand, they were on the lower floors of the hotel, and Anita was not,” he said.

Abel said the company has a “very, very rigorous” security policy and does safety assessments of hotels where its employees stay; the company trains employees to handle emergencies. The Radisson Blu, he said, “was considered a safe hotel.”

He described Datar as “brilliant” and “a true inspiration” to younger associates. “Her work had real impact and touched many people’s lives in the countries in which she worked,” he said.

Former secretary of state Hillary Clinton also praised Datar’s work. Datar’s ex-husband, David Garten, was one of Clinton’s policy advisers when she served in the Senate.

“Anita Datar was a bright light who gave help and hope to people in need around the world, especially women and families. . . . She represented the best of America’s generous spirit,” Clinton said in a statement.

“My prayers are with the Datar and Garten families, especially Anita and David’s son,” Clinton said. “My heart breaks thinking of the burden he will now bear on his small shoulders and the courage he will have to show in the days ahead.”

People who knew Datar spoke about her passion for her son, Rohan, a student at Takoma Park Elementary School. His photos are prominent on her Facebook page, where he is shown smiling on his bike and mugging for the camera with his arm around his mom. On Sundays, she cooked organic meals for him for the week.

As friends gathered Saturday to grieve at Dougherty’s home in ­Takoma Park, they described a beautiful woman inside and out.

Anupa Deshpande, another colleague, said Datar approached everyone as a friend. “Her first thought about someone was their goodness,” Deshpande said. “She was a very open person that way.”

Two days before she was killed, Datar wrote on Facebook about the terrorism and violence that had gripped Paris and the world. “This is an everyday reality for so many worldwide, including folks in Mali,” she said. “Doesn’t diminish the horrors of the Paris bombing; just wish more people realized that many parts of the world live in real fear, and it isn’t just ‘something terrible that happened.’ ”

Although she was devoted to improving the lives of others, ­Datar also knew how to have fun, hosting many girls’ nights out at her home, her friends said. She had a pink hot tub at her house and a memorable laugh.

“Waking up this morning,” mourned one friend on Facebook, “and learning that I won’t ever hear Anita’s laugh again is devastating.”

Matt Zapotosky, Joe Heim, Perry Stein, Jennifer Jenkins and Alice Crites contributed to this report.