PRESCOTT, ARIZONA (REUTERS) - Ms Kayla Mueller, the young United States aid worker who died while a captive of militants of the Islamic State in Iraq and Syria (ISIS), was remembered by family and friends in her hometown on Tuesday as a "free spirit" driven by her enormous empathy for human suffering.
Ms Mueller, 26, was confirmed to have died under circumstances that remain unclear about 18 months after she was abducted while leaving a hospital in northern Syria.
The White House said Ms Mueller's family received a message from her captors containing information that was authenticated by US intelligence analysts who verified her death .
President Barack Obama also publicly acknowledged in an interview with the news website Buzzfeed that Ms Mueller was among the hostages whom US commandos were sent to rescue but failed to find in an operation he ordered last year.
Outside the county courthouse in her hometown of Prescott, Arizona, two of Ms Mueller's maternal aunts joined one of her childhood friends and a local pastor to deliver a tearful tribute to the Northern Arizona University grad.
"She had a quiet, calming presence. She was a free spirit, always standing up for those who were suffering and wanting to be their voice," Ms Lori Lyon said of her niece in a statement.
"Kayla had such great empathy, and it's hard to find that in this world. It's really rare, and it was her greatest strength," said Ms Eryn Street, who described Mueller as her closest friend and "kindred spirit".
Ms Kathleen Day, head of the United Christian Ministry at Northern Arizona University, related accounts of how Ms Mueller's upbeat mood prevailed even in captivity, as she tried to teach origami to her guards, and exercised in cramp quarters by doing headstands.
Near the courthouse just off the main town square stood a small, makeshift shrine adorned with flowers, a cross, a toy bear and a handwritten note: "God bless you Kayla."
A large white sign with the words "Pray for Kayla" stood beside it.
Prescott Mayor Marlin Kuykendall, a friend of the Muellers, said there had been talk of a memorial service, but that will take some time and be dictated by the wishes of her family.
Before her abduction, Ms Mueller worked for a Turkish relief agency on the Syrian border, first traveling to that region in 2012. She previously had volunteered for schools and relief groups elsewhere in the Mideast and India.
"Kayla was a compassionate and devoted humanitarian. She dedicated the whole of her young life to helping those in need of freedom, justice and peace," her parents, Marsha and Carl, said in a statement.
Ms Lyon and others expressed hope that news of her fate might rally more Americans to the cause of those suffering in conflicts around the globe.
"The world grieves with us. The world mourns with us. The world wants to be more like Kayla, and if that is her legacy and the footprint she leaves on the world, then that is a wonderful thing," Ms Lyon said between sobs.