The American aid worker held hostage by Islamic State militants has been killed, her parents and the White House confirmed yesterday (Tuesday).
"We are heartbroken to share that we've received confirmation that Kayla Jean Mueller, has lost her life," Carl and Marsha Mueller said in a statement. "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."
The confirmation came four days after Islamic State of Iraq and the Levant (Isil) said 26-year-old Miss Mueller had been killed in a Jordanian air strike launched following the burning to death of a Jordanian pilot by the terrorists.
US officials were unable to immediately confirm the cause of her death.
Miss Mueller's parents released a letter that their daughter had written to them while in captivity.
"I have been shown in darkness, light + have learned that even in prison, one can be free," she wrote in the letter, which was smuggled out by fellow captives following their release by Isil.
"I could only but write the letter a paragraph at a time, just the thought of you all sends me into a fit of tears. I know you would want me to remain strong. That is exactly what I am doing."
She concluded by looking forward to a reunion that was never to take place. "The thought of your pain is the source of my own, simultaneously the hope of our reunion is the source of my strength."
President Barack Obama said that Miss Mueller, an aid worker who assisted humanitarian organisations working with Syrian refugees, "epitomised all that is good in our world", adding: "No matter how long it takes, the United States will find and bring to justice the terrorists who are responsible for Kayla's captivity and death."
Miss Mueller was taken hostage in August 2013 while leaving a hospital in Syria. John Cantlie, a British journalist, is the last known Western captive held by Isil.
Earlier, Bashar al-Assad, Syria's president, disclosed that his government was regularly informed by America about its plans for air strikes on Isil jihadists.
Despite Washington publicly calling for Mr Assad's downfall, the Pentagon let Damascus know when its warplanes were operating in rebel-held areas of northern Syria, Mr Assad told the BBC.
To avoid diplomatic embarrassment to either side, the communications were normally done via third nations such as neighbouring Iraq.
While Mr Assad denied that it amounted to "direct cooperation", he conceded that it had stopped US and Syrian warplanes colliding or firing on one another.
Mr Assad's remarks demonstrate how Washington has shifted in its perception of the principal threat in Syria. Previously, its sole focus was in getting rid of Mr Assad. Now the danger from Isil is deemed the greater of two evils.
Although the Assad regime has long portrayed itself as under threat from Isil, Western diplomats suspect that Damascus actually helped to nurture the growth of radical Islamist groups, releasing scores of jihadist detainees from prison.
The regime is thought to have calculated that the threat of coming under harsh Islamist rule would push Syrians back into the arms of Mr Assad, a gamble that appears to have had some success.