A new graphic video by the militant Islamic State group claims that U.S. aid worker Peter Kassig has been beheaded. Kassig, 26, was captured last year while helping provide medical aid to Syrians. His friends say he converted to Islam in captivity and changed his name to Abdul-Rahman. The video also showed what appeared to be the mass beheading of several captured Syrian soldiers. It was not immediately possible to confirm that Kassig was pictured in the video.