The Ecclesiastical History of Socrates Scholasticus

Magnentius in the meanwhile having made himself master of the imperial city Rome, put to death many members of the senatorial council, as well as many of the populace. But as soon as the commanders under Constantius had collected an army of Romans, and commenced their march against him, he left Rome, and retired into the Gauls. There several battles were fought, sometimes to the advantage of one party, and sometimes to that of the other: but at last Magnentius having been defeated near Mursa—a fortress of Gaul—was there closely besieged. In this place the following remarkable incident is said to have occurred. Magnentius desiring to reassure the courage of his soldiers who were disheartened by their late overthrow, ascended a lofty tribunal for this purpose. They, wishing to give utterance to the usual acclamation with which they greet emperors, contrary to their intention simultaneously all shouted the name not of Magnentius, but of Constantius Augustus. Regarding this as an omen unfavorable to himself, Magnentius immediately withdrew from the fortress, and retreated to the remotest parts of Gaul. Thither the generals of Constantius hastened in pursuit. An engagement having again taken place near Mount Seleucus, Magnentius was totally routed, and fled alone to Lyons, a city of Gaul, which is distant three days’ journey from the fortress at Mursa. Magnentius, having reached this city, first slew his own mother; then having killed his brother also, whom he had created Cæsar, he at last committed suicide by falling on his own sword. This happened in the sixth consulate of Constantius, and the second of Constantius Gallus, on the fifteenth day of August. Not long after, the other brother of Magnentius, named Decentius, put an end to his own life by hanging himself. Such was the end of the enterprises of Magnentius. The affairs of the empire were not altogether quieted; for soon after this another usurper arose whose name was Silvanus: but the generals of Constantius speedily put him also out of the way, whilst raising disturbances in Gaul.