(VOVworld) – The Islamic State announced in a video posted online on Sunday that they have beheaded US aid worker Peter Kassig.

Peter Kassig, the American citizen held hostage held by Islamic State militants. (Photo: Sera/EPA)

If the video is confirmed, Kassig becomes the third US citizen executed by IS. 26-year-old Kassig was from Indiana. It was said that he converted to Islam during his captivity and changed his name to Abdul Rahman. Kassig was a humanitarian aid worker intent on helping Syrian people. He was captured in October, 2013 while on his way to Deir Al Zor in eastern Syria. In the video, IS claimed to have executed 18 people believed to be soldiers in the Syrian army.