Probus died

Probus was eager to start his eastern campaign, delayed by the revolts in the west. He left Rome in 282, traveling first towards Sirmium, his birth city. Different accounts of Probus's death exist. According to Joannes Zonaras, the commander of the Praetorian Guard Marcus Aurelius Carus had been proclaimed, more or less unwillingly, emperor by his troops. Probus sent some troops against the new usurper, but when those troops changed sides and supported Carus, Probus' remaining soldiers assassinated him at Sirmium (September/October 282). According to other sources, however, Probus was killed by disgruntled soldiers, who rebelled against his orders to be employed for civic purposes, like draining marshes. Allegedly, the soldiers were provoked when they overheard him lamenting the necessity of a standing army. Carus was proclaimed emperor after Probus' death and avenged the murder of his predecessor.