This undated photo shows Peter Kassig standing in front of a truck filled with supplies for Syrian refugees. (Courtesy of Kassig family/Associated Press)

The parents of a captive American aid worker whom the Islamic State threatened to kill last week released a statement Sunday night sharing a portion of a letter from their son.

In Peter Kassig’s letter, sent to his parents in early June, the former Army Ranger says he is “obviously pretty scared to die but the hardest part is not knowing, wondering, hoping, and wondering if I should even hope at all.”

The letter continues:

“I am very sad that all this has happened and for what all of you back home are going through. If I do die, I figure that at least you and I can seek refuge and comfort in knowing that i went out as a result of trying to alleviate suffering and helping those in need.”

The statement from Kassig’s parents also addresses their son’s Muslim faith. In a separate video statement released over the weekend, Kassig’s parents, Ed and Paula Kassig, said their son’s humanitarian work in Syria “culminated in him embracing Islam.” According to his parents, Kassig changed his first name from Peter to Abdul-Rahman upon conversion.

The parents of Peter Kassig, an American aid worker being held hostage by Islamic State militants, released a statement pleading for their son's release. (YouTube/Kassig Family)

On Sunday, Kassig’s parents wrote that “Abdul-Rahman’s journey toward Islam began before he was taken captive,” adding that “he observed the month-long Ramadan fast in July-August 2013 prior to his capture, and spoke of the great impact this spiritual practice had on him.”

Their son, they said, “worked and lived alongside Syrian Muslims before his capture and had come to admire and respect them greatly.”

Kassig disappeared from Raqqah in eastern Syria a year ago while doing humanitarian work in the region. On Friday, the Islamic State revealed that it had Kassig in captivity and threatened to kill the American because of a U.S. bombing campaign against Islamic State targets.

In the same video, an unidentified militant executed British hostage Alan Henning.

The same militant appears to be the person who killed American journalists Steven Sotloff and James Foley and British aid worker David Haines. Those killings were announced via gruesome online videos.

In the letter to his family, written during his captivity, Kassig said: “In terms of my faith, I pray every day and I am not angry about my situation in that sense. I am in a dogmatically complicated situation here, but I am at peace with myself.”

The family, in its statement, added: “We want to send our heartfelt thanks to the many people around the world who have offered their prayers and support to our family at this difficult time.”

Here is the full excerpt from the family, which edited the original letter for length and to omit sensitive information:

The first thing I want to say is thank you. Both to you and mom for everything you have both done for me as parents; for everything you have taught me, shown me, and experienced with me. I cannot imagine the strength and commitment it has taken to raise a son like me but your love and patience are things I am so deeply grateful for.

I am obviously pretty scared to die but the hardest part is not knowing, wondering, hoping, and wondering if I should even hope at all. I am very sad that all this has happened and for what all of you back home are going through. If I do die, I figure that at least you and I can seek refuge and comfort in knowing that I went out as a result of trying to alleviate suffering and helping those in need.

In terms of my faith, I pray everyday and I am not angry about my situation in that sense. I am in a dogmatically complicated situation here, but I am at peace with my belief.

I wish this paper would go on forever and never run out and I could just keep talking to you. Just know I’m with you. Every stream, every lake, every field and river. In the woods and in the hills, in all the places you showed me. I love you.