For over a year and a half the family of Kayla Jean Mueller, a 26-year-old aid worker from Arizona, kept the fact that she was being held in ISIS captivity in Syria a secret from most everyone. While it was known the terrorist organization was holding a young female American among their hostages, the hope of both the U.S. government and Mueller’s family seems to have been that not making her identity public could help in efforts to secure her release.

Last week, however, it was ISIS itself that outed her, announcing Friday that the young woman had been in their captivity – but had been killed by a Jordanian air bombardment on Raqqa, an ISIS stronghold in Syria. The Jordanian Interior Ministry called ISIS’s statement about her death “a stunt,” and for several days the U.S State Department could not verify Mueller’s death, its timing or the circumstances behind it.

But on Tuesday U.S. President Barack Obama confirmed that Mueller had indeed been killed, promising to “find and bring to justice the terrorists who are responsible.”

‘Best smile’

An idealistic, bright eyed girl from the small town of Prescott, who was voted “best smile” in her graduating year and was a member of her high school’s robotics club, Mueller was someone who seems to have always been drawn to helping the weak; always indignant about the unjust.

She organized marches to raise awareness of the situation in Darfur, volunteered with America’s Promise and Big Brothers Big Sisters, was college president of a student-led movement to end mass atrocities, and won the Yavapai County Community Foundation award for Youth Philanthropist of the Year in 2005. The quote on her high school yearbook page comes from William Blake: “No bird soars too high if he soars with his own wings.”

Mueller had been in Syria exactly one day and one night when she was kidnapped, on August 4, 2013. But she was not new to the Middle East or areas of conflict. After graduating from Northern Arizona University in 2009 – after just two and a half years – she set out into the world, traveling and volunteering in northern India and then in Israel and the Palestinian territories.

Defending Palestinians

She apparently spent the hot months of August and September of 2010 volunteering for the International Solidarity Movement, the pro-Palestinian activist group made famous by another American, Rachel Corrie, who had been killed while volunteering with them in 2003 – when an armored Israeli bulldozer demolishing a Palestinian home hit her.

According to the ISM, Mueller worked and lived in the Sheikh Jarrah neighborhood in East Jerusalem, staying with a family called Al-Kurd, “to try and prevent the takeover of their home by Israeli settlers.”

She also worked in Hebron, where, according to the organization, she accompanied Palestinian children to school in the neighborhood of Tel Ruimeda, and stayed in a protest tent, together with villagers of Izbat al-Tabib, to try to prevent the demolition of homes in that village. She also joined weekly Friday protests against the Israeli occupation in Bilin and other Palestinian villages, writing frequent blogs about those experiences.

“Oppression greets us from all angles,” she wrote in one post. “Oppression wails from the soldiers radio and floats through tear gas clouds in the air But resistance is nestled in the cracks in the wall, resistance flows from the minaret 5 times a day and resistance sits quietly in jail knowing its time will come again. Resistance lives in the grieving mother’s wails and resistance lives in the anger at the lies broadcasted across the globe. Though it is sometimes hard to see and even harder sometimes to harbor, resistance lives. Do not be fooled, resistance lives.”

Helping Africans in TA

Mueller also reportedly spent some time in Tel Aviv, volunteering for The African Refugee Development Center, a community-based non-profit dedicated to protecting, helping and empowering African refugees and asylum seekers in Israel.

Representatives from the ARDC said they were looking into whether or not Mueller had, in fact, worked for their organization, but that so far, they could not confirm or deny the news. It is possible, said one ARDC representative, that Mueller was more of an activist on behalf of asylum seekers and not a formal volunteer on their program.

What is known is that after her time in this region, and close to a year back in Arizona – during which Mueller volunteered at an AIDS clinic and a women’s shelter – she traveled as an au pair to Paris to learn French, and then decided to go to Turkey in December 2012. At this point she began volunteering with different aid groups, including the Danish Refugee Council, and an organization called Support To Life, which assists Syrian women and children refugees who have crossed into Turkey.

‘For as long as I live ...’

Mueller had spoken about her experience on the Syrian border on a trip back home, at the local Kiwanis Club, where her father was a member. “When Syrians hear I’m an American, they ask, ‘Where is the world?’” she told those gathered, as reported in the local paper. “All I can do is cry with them, because I don’t know,” she said. “For as long as I live, I will not let this suffering be normal.” The blog she kept during this period was called “Imbued with Hope.”

Mueller reportedly entered Syria not under any aid organization’s auspices, but with her boyfriend, a Syrian activist and photographer she had met in Cairo. The boyfriend, whose name has not been made public, was reportedly hired as a technician to perform repairs at a Spanish MSF (Doctors without Borders) hospital in Syria.

The work at MSF took longer than the few hours predicted, forcing the couple to spend the night inside Syria. The next day, the charity says it organized transportation to the Aleppo station where the two were meant to take a bus back to Turkey. But they never arrived at the station. Mueller’s boyfriend and two other Syrians were initially also taken hostage, but released. Some accounts say that after his release, Mueller’s boyfriend re-entered Syria to personally plea for his partner to be set free.

Parents’ pleas

Mueller’s parents, Carl and Marsha Mueller, had held out hope for her survival for days after ISIS’s announcement Friday, directing all their pleas at her captors.

“To those in positions of responsibility for holding Kayla; in adherence to your warnings and out of concern for Kayla’s safety, we have been silent until now,” they said in a statement released Friday, hinting at previous direct communication with ISIS. The terror organization has been known to try and circumvent U.S. policy of non-negotiation and demand enormous ransoms for the return of prisoners – directly from their families. CBS News reported that ISIS had demanded a ransom of $6.6 million for Kayla.

“You told us that you treated Kayla as your guest, as your guest her safety and well-being remains your responsibility. Kayla’s mother and I have been doing everything we can to get her released safely,” continues the parents’ plea. “At this time we ask you, who are holding Kayla, to contact us privately.”

Yesterday, however, Mueller’s parents, along with her brother Eric, released a more somber statement, saying they had received confirmation of her death, and that they were “heartbroken.” According to various media reports, the family was sent, over email, a photo of their daughter’s body.

“We are so proud of the person Kayla was, and the work that she did while she was here with us,” the Mueller parents said, according to AP. “She lived with purpose, and we will work every day to honor her legacy.”

The family also made public a poignant hand-written note which they received from their daughter during her 18-month captivity:

“I have been shown in darkness, light + have learned that even in prison, one can be free. I am grateful,” Mueller writes to her family. “I have come to see that there is good in every situation, sometimes we just have to look for it.”

A photocopy of a letter the Mueller family says was written to them by Kayla Jean Mueller in spring 2014. (Reuters/Mueller family)