The caliph Al-Musta'sim was captured and forced to watch as his citizens were murdered and his treasury plundered. According to most accounts, the caliph was killed by trampling. The Mongols rolled the caliph up in a rug, and rode their horses over him, as they believed that the earth would be offended if it were touched by royal blood. All but one of Al-Musta'sim's sons were killed, and the sole surviving son was sent to Mongolia, where Mongolian historians report he married and fathered children, but played no role in Islam thereafter (see The end of the Abbasid dynasty).