On 18 September , 96 , Domitian was assassinated in a palace conspiracy organised by court officials . The Fasti Ostienses , the Ostian Calendar , records that the same day the Senate proclaimed Marcus Cocceius Nerva emperor . Despite his political experience , this was a remarkable choice . Nerva was old and childless , and had spent much of his career out of the public light , prompting both ancient and modern authors to speculate on his involvement in Domitian 's assassination .