Family Mourns Death of ISIS Hostage, 1 Year Later

The family of slain ISIS hostage Kayla Mueller today honored the life of the young woman from Arizona and called on Americans to remember "those lives lost in terrorism and those still missing and held against their will."

"It was one year ago this week ISIS announced the death of our only daughter, sister and friend, 26-year-old Kayla Jean Mueller after 18 months of forced captivity," Mueller's parents said in a statement provided to ABC News. "Kayla was given a special heart and mind not to only see suffering in its many forms but to reach out and find a way to help those God placed before her. Never deterred, yet always determined to help where she could, Kayla is honored today and always through various efforts.

"We do not know why she was taken from us, but her uncrushable spirit and her compassionate heart, her unwavering desire to help others through peace and justice will be with us always and will lead us to the truth. We believe and will always say: 'Kayla should be here,'" they said.

The Syria-based terror group ISIS announced Mueller's death in early February 2015, a claim confirmed by President Obama with "profound sadness" days later. ISIS claimed Mueller had been killed in a U.S.-led coalition airstrike, but U.S. officials disputed that at the time.

Months later U.S. officials told ABC News they believed that Mueller had been repeatedly sexually abused by ISIS leader Abu Bakr al-Baghdadi while being held captive in the home of another high-level ISIS figure.

Mueller, from Prescott, Ariz., was kidnapped in August 2013 after leaving a Spanish Doctors Without Borders hospital in Aleppo, Syria, according to information provided by a family spokesperson.

She had graduated from Northern Arizona University in 2009 and "has devoted her career to helping those in need in countries around the world," the family spokesperson said after her death was confirmed.

Mueller told her town's local newspaper, The Daily Courier, she felt called to help those suffering the most in the midst of the Syrian conflict.

"For as long as I live, I will not let this suffering be normal," she said in the May 2013 report. "[I will not let this be] something we just accept... It's important to stop and realize what we have, why we have it and how privileged we are. And from that place, start caring and get a lot done."

Mueller's parents said today, "In honoring Kayla we also ask that you remember those lives lost in terrorism and those still missing and held against their will. Kayla would want us to lift up and celebrate all those who have been freed and their families. She would want us to honor all those who have served our country so that we may be free. We must never forget those who have sacrificed their lives, the wounded still trying to get their lives back, and their families and friends.

"Our hearts break for Kayla and all that happened, but we know from her letters that God was with her and she is with God. Her letters were such a gift to us -- just like our 'Special K' to send us what we would need to carry on. She was a remarkable young lady who always looked to see what she could do to make this world a better place."

Mueller's parents said the "heartbreaking story" of their efforts to bring Mueller home and of the people who helped and "hindered" them "will be told." The Muellers did not go into detail about who had "hindered" them, but U.S. officials have come under fire from the families of other hostages over U.S. hostage policy.

The family spokesperson said that several charitable efforts are ongoing in memory of Mueller, including The Kayla's Hands Foundation and the Prescott Kiwanis Foundation, which is working to build a playground in Mueller's name.