BREAKING: ISIS Beheads Next American Hostage In Most Brutal Beheading Yet [VIDEO] According to recent reports, Islamic State militants have beheaded yet another U.S. aid worker. This time they brutally took the life of 26-year-old Peter Kassig, even though he converted to Islam. The video was then posted across several social media channels. Kassig served in Iraq in 2007 before becoming a medical technician. He had also volunteered in Palestinian refugee camps offering his services as a trauma medic to Syrian refugees wounded in the fighting in Syria. Kassig was reportedly captures in October of last year by Islamic State militants on his way to the city of Deir Ezzour in eastern Syria. Under pressure from his captures, Kassig converted to Islam and took the name Abdul-Rahman. The footage shows Jihadi John murdering Kassig. The video comes despite reports that the extremist was wounded in an airstrike last week. This time, the footage is 15 minutes long, showing the beheading over several other men in addition to Kassig. The men were reportedly officers serving under Syrian President Bashar Assad. The extremists in the video warn US, UK, and other countries that this may not be the last time. US authorities say that are working as quickly as possible to determine its authenticity. If confirmed, we are appalled by the brutal murder of an innocent American aid worker and we express our deepest condolences to his family and friends, added spokeswoman Bernadette Meehan from the U.S. National Security Council. 