His death was variously attributed to disease, the effects of lightning, or a wound received in a campaign against the Huns; but it seems more probable that he was murdered by the soldiers, who were averse from further campaigns against Persia, at the instigation of Arrius Aper, prefect of the praetorian guard.
Arrius Aper, praefect of the praetorian guards, his father-in-law, who was suspected of having murdered him, was slain by Diocletian, whom the soldiers had already proclaimed his successor.
After the death of Numerianus he was chosen emperor by the troops at Chalcedon, on the 17th of September 28 4, and slew with his own hands Arrius Aper, the praefect of the praetorians.
He thus fulfilled the prediction of a druidess of Gaul, that he would mount a throne as soon as he had slain a wild boar (aper).