Ammianus Marcellinus Res Gestae 14.1.10

[10] Now at that time Thalassius was the Praetorian Prefect at court, ¹ a man who was himself of an imperious character. He, perceiving that Gallus’ temper was rising, to the peril of many, did not try to soothe it by ripe counsel, as sometimes high officials have moderated the ire of princes; but rather roused the Caesar to fury by opposing and reproving him at unseasonable times; very frequently he informed the emperor of Gallus’ doings, exaggerating them and taking pains—whatever his motive may have been—to do it openly. Through this conduct the Caesar was soon still more violently enraged, and as if raising higher, as it were, the standard of his obstinacy, with no regard for his own life or that of others, he rushed on with uncontrollable impetuosity, like a swift torrent, to overthrow whatever opposed him.