Zosimus, New History 2.43

Zosimus (Greek Ζώσιμος): Early Byzantine, pagan author of a history of the Roman Empire, published in the first quarter of the sixth century CE.

The translation of ZosimusNew History offered here was printed in 1814 by W. Green and T. Chaplin in London, and was probably prepared by J. Davis of the Military Chronicle and Military Classics Office. The translator is anonymous. The text was found at Tertullian.org. The notes were added by Jona Lendering.

[2.43.1] Magnentius thus gained the empire, and possessed himself all the nations beyond the Alps, and the whole of Italy. Vetranio, general of the Pannonian army, upon hearing of the good fortune of Magnentius, was himself inflamed with the same desire, and was declared emperor by the legions that were with him, at Mursa, a city of Pannonia. While affairs were thus situated, the Persians plundered the eastern countries, particularly Mesopotamia. But Constantius, though he was defeated by the Persians, yet resolved to subdue the factions of Magnentius and Vetranio. 

[2.43.2] While he was forming these resolutions, and was very intent on warlike preparations, Magnentius still remaining in Gallia Celtica, Nepotianus, nephew to Constantius by his sister Eutropia, collected a band of persons addicted to robbery and all kinds of debauchery, with whom he came to Rome, and appeared in an imperial dress. 

[2.43.3] Anicetius, whom Magnentius had made prefect of the court, armed some of the common people, and led them out of the city to engage with Nepotianus. A sharp conflict ensued between them. The Romans being undisciplined, and observing no order, were easily routed; and when the prefect saw them fly, he shut the gates, for fear the enemy should follow them into the city. 

[2.43.4] The troops of Nepotianus pursued them, and as they had no way of escape, killed every man. In a few days after, Magnentius sent an army under the command of Marcellinus, and Nepotianus was put to death.