American Aid Worker Kassig in ISIS Video 'Scared to Die'

— -- An American aid worker threatened with beheading by the terror group ISIS is afraid to die – and saddened by the impact his imprisonment is having on his parents, he wrote in a letter his parents released Sunday.

Abdul-Rahman Kassig, 26, thanked his parents, Ed and Paula Kassig, for their support in the letter, which they say was received June 2. Kassig was previously known as Peter, but his family requested that he be identified as Abdul-Rahman due to his conversion to Islam.

“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,” he wrote in the letter, according to his parents. “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 the letter, Kassig described his situation as “dogmatically complicated.”

“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,” he wrote to his parents.

The statement released Sunday includes family photographs: Kassig fishing with his father in 2011; a young Kassig with his mother; Kassig working as a medic; Kassig helping to push an ambulance up a hill.

The Indiana native was seen at the end of a video that emerged online Friday in which a purported ISIS militant murdered British captive Alan Henning. Kassig served as an Army Ranger in the Iraq war and later became an emergency medical technician, volunteering as a medical assistant in Lebanon in 2012. He was abducted in October 2013, while traveling to a town in eastern Syria for SERA – Special Emergency Response and Assistance, a non-governmental organization he founded.

After the ISIS video emerged, Kassig’s parent’s released a video statement pleading for their son’s release.

“Most of all, know that we love you, and our hearts ache for you to be granted your freedom so we can hug you again and then set you free to continue the life you have chosen, the life of service to those in greatest need," Paula Kassig said in the video. "We implore those who are holding you to show mercy and use their power to let you go."

ISIS has killed four Western hostages on camera previously: American journalists James Foley and Steven Sotloff, and British aid workers David Haines and Henning.