10/02/2015 15:34 GMT | Updated 10/02/2015 16:59 GMT

Kayla Mueller's Family Sent Confirmation Of Her Death By Islamic State

The family of Kayla Mueller, the 26-year-old aid worker held hostage by Islamic State, say they have received confirmation of her death and a picture of her.

The Islamic State group said Friday that Mueller had died in a Jordanian airstrike, and communicated with her family over the weekend, giving them information about her death which the US government said it had authenticated.

“We are heartbroken to share that we’ve received confirmation that Kayla Jean Mueller, has lost her life,” a statement on behalf of her parents Marsha and Carl Mueller said. “Our hearts are breaking for our only daughter, but we will continue on in peace, dignity, and love for her.”

mueller mother

'Still Hopeful': Parents of Islamic State hostage Kayla Mueller ask the militant group for contact

The family have also released a hand-written note sent to them during her captivity, with a jagged edge torn from a notebook.

It reads:

"Everyone, if you are receiving this letter it means I am still detained but my cell mates (starting from 11/2/2014) have been released. I have asked them to contact you and send you this letter. It is hard to know what to say. Please know that I am in a safe location completely unharmed and healthy (put on weight in fact). I have been treated with the upmost respect and kindness. I wanted to write you all a well-thought-out letter (but I didn't know if my cell mates would be leaving in the coming days or the coming months restricting my time but primarily I could only write the letter a paragraph at a time).

"Just the thought of you all sends me into a fit of tears. If you could say I have "suffered" at all throughout this whole experience it is only knowing how much suffering I have put you all through. I will never ask you to forgive me as I don't deserve your forgiveness. I remember mom always telling me that all in all and in the end, the only one you really have is God. I have come to a place in this experience where, in every sense of the word, I have surrendered myself to our creator because literally there was no one else.

"And by God and by your prayers I have been tenderly cradled in free fall, I have been shown in darkness, light and have learned that even in prison, one can be free. I am grateful. I have come to see that there's good in every situation, sometimes we just have to look for it. I pray each day that if nothing else you have felt a certain closeness and surrender to god as well and formed a bond of love and support amongst one another.

"I miss you all as if it has been a decade of forced separation. I have had many a long hour to think, to think, to think of all the things I will do, our first family camping trip, the first meeting at the airport. I have had many hours to think how only in your absence have I finally, at 25-years-old come to realise your place in my life. The gift that is each one of you and the person I could and could not be if you were not a part of my life, my family, my support.

"I DO NOT want the negotiations for my release to be your duty, if there is any other option take it, even if it takes more time. This should never have become your burden. I have asked these women to support you, please seek their advice. If you have not done so already xxx [redacted] can contact xxx [redacted] who may have a certain lever of experience with these people. None of us could have known it would be this long but know I am also fighting from my side in the ways I am able and I have a lot of fight left inside of me.

"I am not breaking down and I will not give in no matter how long it takes. I wrote a song some months ago that says "the part of me that pains the most also gets me out of bed, without your hope there would be nothing left." aka - The thought of your pain is the source of my own, simultaneously the hope of our reunion is the source of my strength. Please be patient, give your pain to God. I know you would want me to remain strong that is exactly what I am doing. Do not fear for me. Continue to pray as will I and by God's will, we will be together soon.

All my everything, Kayla"

President Barack Obama said that Mueller, who worked with Syrian refugees, "epitomised all that is good in our world."

"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," the president said.

Mueller was the only known remaining US hostage held by the Islamic State group. She was taken into captivity in August 2013 while leaving a hospital in Syria.

US vice-president Joe Biden also paid tribute to the young aid worker, calling her "a compassionate young American who represented everything good about the human spirit".

"There are no words to express to Kayla's parents, Marsha and Carl, how sorry we are for their crushing loss, just how much so many wished for and worked to try and secure a better outcome, or how awe-inspiring is the example of their strength, determination, and devotion to faith and family," he continued. "To them, and to Kayla's brother Eric and his family, I hope they can know that our entire country grieves together with all those whose lives she touched."

Mueller had "one mission in life from the very start, and that was to help people," Biden said. She worked on aid projects in India, Israel, and the Palestinian Territories, with people at an HIV/AIDS clinic and a women’s shelter at home in Arizona, and, most recently, Syrian refugees in Turkey.

She was active in campaigning for Darfur during her university years, writing letters, lobbying members of Congress, and conducting two silent walks. Her high school teacher told a local paper at the time that he could envision a then 19-year-old Mueller "running an activism group, or getting involved in national or international politics."

She worked in Turkey and Syria with the international humanitarian aid agency Support to Life. In an article published in her local paper The Daily Courier before she was kidnapped, Mueller pleaded for aid for those she was helping.

"Syrians are dying by the thousands, and they're fighting just to talk about the rights we have," Mueller said. "For as long as I live, I will not let this suffering be normal, something we just accept. It's important to stop and realise what we have, why we have it and how privileged we are. And from that place, start caring and get a lot done."