According to Adnan Oktar, the first period is said to have begun with the death of Muhammad. The second began with the passing of all his Companions, and ended a thousand years later. Another event of the second period was the Tartar invasion, occurring 650 years after Muhammad. The Mongols, led by Hulagu Khan, grandson of Genghis Khan, attacked Baghdad in 1258 AD and brought the Abbasid caliphate to an end. They massacred millions of Muslims, and the water of the river Tigris turned red with blood. A traditional narration also predicted a fire at Madinah in the Hijaz near Busra in Syria, which Islamic scholars believe occurred in 654 AH. Following the second, the third and final period will be heralded by the appearance of the Mahdi.