Kayla Mueller, an American humanitarian worker who had been held hostage by ISIS since 2013, has died, her family confirmed Tuesday. Reuters/Courtesy Mueller family

Friends and family of Kayla Mueller spoke to reporters Tuesday in a teary press conference from her hometown of Prescott, Arizona, describing a young woman of deep conviction and empathy who had traveled to Syria in the hopes of shining a light on atrocities there.

Mueller, the 26-year-old American aid worker who was abducted by ISIS in 2013, was confirmed dead Tuesday by her parents, who said they received a message from the terrorist group containing photographic proof.

Kathleen Day, one of Mueller’s mentors at Northern Arizona University, told reporters Mueller had written blog posts from Syria, describing the horrendous conditions in the civil war-torn country and saying that every human being should act to help put an end to the suffering. “I want to tell the world about the situation in Syria,” Mueller wrote.

Eryn Street, a childhood friend of Mueller's, said empathy was her “greatest strength.” Street broke out in tears as she read a quote from Mueller: “Peace is not something you wish for. It’s something you make. It’s something you do. It’s something you are. And it’s something you give away.”

It’s still unclear how Mueller died. Last week, ISIS claimed she was killed in a Jordanian air strike, but U.S. officials said the group offered no proof. Mueller was believed to be the last American hostage held by ISIS.

During Tuesday’s press conference, one of Mueller’s aunts said Mueller spent her life standing up for people who are suffering, wanting to “be their voice.” “Kayla did more in 26 years than most do in a lifetime,” she said.

In a statement earlier on Tuesday, the White House said Mueller “dedicated her life to helping others in need at home and around the world.”

Christopher Zara is a senior writer who covers media and culture. News tips? Email me here. Follow me on Twitter @christopherzara.