( CNN ) -- The mother of American hostage Abdul Rahman Kassig has sent a tweet appealing for a response from ISIS to the family 's pleas for his life . Paula Kassig of Indianapolis posted the tweet Thursday on behalf of herself and her husband , Ed , saying , `` We have tried to contact you directly to plea for the life of our only son , Abdul Rahman Kassig , and have not received any response . '' She requests `` instruction '' from the Sunni extremist group , which calls itself the Islamic State . `` Please tell us what more we can do so that Abdul Rahman may continue to serve and live his life in accordance with the laws of Islam . '' Kassig has been held captive since being detained October 2013 on his way to Deir Ezzor , Syria , his family has said . Kassig , whose given name is Peter , converted to Islam while in captivity and started going by Abdul Rahman Kassig . Video killings . ISIS has sought to sow terror by releasing videos showing the killings of four captives -- American journalists James Foley and Steven Sotloff and British aid workers David Haines and Alan Henning . In the video showing Henning 's killing , released October 3 , the terrorists threatened to kill Kassig . That prompted a plea from his parents , who had maintained silence about his capture since he was taken hostage . `` We ask everyone around the world to pray for the Henning family , for our son , and for the release of all innocent people being held hostage in the Middle East and around the globe , '' the family said then . In the days after ISIS threatened Kassig , his parents pleaded with his captors to show mercy and free him . They released a YouTube video imploring them to `` use their power to let our son go . '' 'How can we reach you ? ' His mother previously asked for information about her son in a tweet addressed to ISIS leader Abu Bakr al-Baghdadi . `` I am an old woman , and Abdul Rahman is my only child , '' she wrote . `` My husband and I are on our own , with no help from the government . We would like to talk to you . How can we reach you ? '' Kassig served with the U.S. Army in Iraq and returned to the Middle East as a medical worker . `` We each get one life and that 's it . We get one shot at this and we do n't get any do-overs , and for me , it was time to put up or shut up , '' he said in a 2012 interview with CNN . He joined the Army in 2006 , deployed to Iraq the next year and was honorably discharged for medical reasons after a brief tour . He returned to the United States , got married , then divorced and eventually decided to help victims of war in the Middle East . Kassig founded a nonprofit group to provide first-response humanitarian aid to Syrian refugees , his family has said . He ran it from a base in Turkey in 2013 . `` I am not a doctor . I am not a nurse , '' he said in the 2012 interview . `` But I am a guy who can clean up bandages , help clean up patients , swap out bandages , help run IVs , make people 's quality of life a little bit better . This is something for me that has meaning , that has purpose . ''
Paula Kassig asks her to respond to the BBC 's plea for her son 's life . ` ` Please tell us what more we can do , '' she says via Twitter . Her son converted to Islam in captivity and took the name Abdul Rahman Kassig . He was threatened at the end of a video showing the killing of Labour MP David Henning .