ISIS' American hostage confirmed dead

Feb 10, 2015, 4:40 PM EST
Ruins in Aleppo, Syria (ZEIN AL-RIFAI/AFP/Getty Images)

Kayla Mueller, the aid worker believed to be the last remaining American captive of the Islamic State, was confirmed dead by her family as well as U.S. officials Tuesday. Reuters reports that President Barack Obama has vowed to "find and bring to justice the terrorists who are responsible." 

While ISIS claimed Friday that Mueller was killed in a Jordanian air strike outside the city of Raqqa, the actual cause of Mueller's death is still unknown. The Islamic State provided no photographic evidence to back-up their story, and U.S. officials doubt the allegations. Two government officials reportedly believe that Mueller was killed "in some kind of combat situation in which her captors were unable to keep her safe." According to U.S. Secretary of State John Kerry, "ISIL, and ISIL alone, is the reason that Kayla is gone." 

Mueller was working to provide humanitarian aid through the organization Doctors Without Borders in Aleppo, Syria when she was kidnapped in 2013. The Washington Post reports that her family released a handwritten letter that Kayla wrote to them from captivity in 2014. In the two-page document, Mueller assured them she was "in a safe location, completely unharmed + healthy" and has been "treated w/ the utmost respect and kindness." She went on to say that "I have been shown in darkness, light + have learned that even in prison, one can be free." 

Mueller was 25 years old and had dedicated her life to humanitarian work, ABC News reports. Since her graduation from Northern Arizona University in 2009, she had also worked in India and Palestine. "We are so proud of the person Kayla was and the work she did while she was here with us," her family said in a statement. "She lived with purpose, and we will work every day to honor her legacy."