Ecclesiastical history (Sozomen)/Book IV/Chapter VII
Death of the Tyrants Magnentius and Silvanus the Apostate. Sedition of the Jews in Palestine. Gallus Caesar is Slain, on Suspicion of Revolution.
In the meantime, Magnentius made himself master of ancient Rome, and put numbers of the senators, and of the people, to death. Hearing that the troops of Constantius were approaching, he retired into Gaul; and here the two parties had frequent encounters, in which sometimes the one and sometimes the other was victorious. At length, however, Magnentius was defeated, and fled to Mursa, which is the fortress of this Gaul, and when he saw that his soldiers were dispirited because they had been defeated, he stood on an elevated spot and endeavored to revive their courage. But, although they addressed Magnentius with the acclamations usually paid to emperors, and were ready to shout at his public appearance, they secretly and without premeditation shouted for Constantius as emperor in place of Magnentius. Magnentius, concluding from this circumstance, that he was not destined by God to hold the reins of empire, endeavored to retreat from the fortress to some distant place. But he was pursued by the troops of Constantius, and being overtaken at a spot called Mount Seleucus, he escaped alone from the encounter, and fled to Lugduna. On his arrival there, he slew his own mother and his brother, whom he had named Caesar; and lastly, he killed himself. Not long after, Decentius, another of his brothers, put an end to his own existence. Still the public tumults were not quelled; for not long after, Silvanus assumed the supreme authority in Gaul; but he was put to death immediately by the generals of Constantius.
The Jews of Diocaesarea also overran Palestine and the neighboring territories; they took up arms with the design of shaking off the Roman yoke. On hearing of their insurrection, Gallus Caesar, who was then at Antioch, sent troops against them, defeated them, and destroyed Diocaesarea. Gallus, intoxicated with success, could not bear his prosperity, but aspired to the supreme power, and he slew Magnus, the quaestor, and Domitian, the prefect of the East, because they apprised the emperor of his innovations. The anger of Constantius was excited; and he summoned him to his presence. Gallus did not dare to refuse obedience, and set out on his journey. When, however, he reached the island Elavona he was killed by the emperor's order; this event occurred in the third year of his consulate, and the seventh of Constantius.