Family, friends and State Department colleagues on Sunday were mourning the first death of a diplomat on duty since Ambassador Chris Stevens was killed in the attack on the U.S. Consulate in Benghazi, Libya on Sept. 11 last year.
Anne Smedinghoff, 25, was one of five Americans killed in a car bomb attack on Saturday in Zabul Province, Afghanistan, Secretary of State John Kerry said Sunday. Three of the dead were U.S. service members and the fifth a civilian employee of the Defense Department, Kerry said.
They had not been named as of Sunday morning.
Several Afghans and four other State Department employees were injured, one critically.
A sixth American civilian working with the U.S. government was killed in a separate attack in eastern Afghanistan on Saturday, ISAF said in a statement.
"It's a grim reminder to all of us, though we didn't need any reminders, of how important and also how risky carrying the future is with people who want to resist," Kerry told State Department employees on Sunday during a visit in Istanbul, Turkey.
Smedinghoff and the other Americans were traveling in a convoy to southern Afghanistan to deliver textbooks to children in Qalat, Kerry said.
He met the Illinois-native several weeks ago when she worked as his control officer during his recent trip to Afghanistan. He described her as "vivacious, smart, capable."
"There are no words for anyone to describe the extraordinary harsh contradiction for a young 25-year-old woman, with all of her future ahead of her, believing in the possibilities of diplomacy to improve people's lives, making a difference, having an impact" to be killed, Kerry said.
Smedinghoff previously served in Venezuela.
In an email to the Washington Post, Smedinghoff's parents said their daughter "was always looking for opportunities to reach out and help to make a difference in the lives of those living in a country ravaged by war."
They added: "We are consoled knowing that she was doing what she loved, and that she was serving her country by helping to make a positive difference in the world."
Smedinghoff recently helped NBC News coordinate a report on "Buzkashi Boys," the short film nominated for an Oscar starring an Afghan boy who was discovered on the streets of Kabul. Local Afghan producer Khyber Shinwari described her as "a lovely lady, charming – smiling on her face."
"She was very open and so helpful. So kind," he said. "She was here to help Afghans."
The Taliban claimed responsibility for the Zabul attack in a text message Saturday. The assault came just three days after 54 people were killed in another Taliban attack on a courtroom in the western Farah province of Afghanistan.
The United Nations has said civilians are increasingly being targeted this year.
On his first day in office, Kerry said the safety of State Department employees was a top priority, in the wake of the attack that killed Ambassador Stevens and three other Americans in Benghazi. No one has been convicted as of yet.
NBC News' Jamieson Lesko, Kiko Itsaka and Catherine Chomiak, and The Associated Press and Reuters contributed to this report.
Related:
'We have to go': Afghans ready to flee country as foreign troops withdraw
54 killed, 90 wounded in attack on Afghan compound
Tears of joy: The moment an Afghan teen learned of Oscar nomination