Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[17] Now there were three several conspiracies made in order to take off Caius, and each of these three were conducted by excellent persons. Emilius Regulus, born at Corduba in Spain, got some men together, and was desirous to take Caius off, either by them or by himself. Another conspiracy there was laid by them, under the conduct of Cherea Cassius, the tribune [of the Pretorian band]. Minucianus Annins was also one of great consequence among those that were prepared to oppose his tyranny. Now the several occasions of these men's several hatred and conspiracy against Caius were these: Regulus had indignation and hatred against all injustice, for he had a mind naturally angry, and bold, and free, which made him not conceal his counsels; so he communicated them to many of his friends, and to others who seemed to him persons of activity and vigor: Minucianus entered into this conspiracy, because of the injustice done to Lepidus his particular friend, and one of the best character of all the citizens, whom Caius had slain, as also because he was afraid of himself, since Caius's wrath tended to the slaughter of all alike: and for Cherea, he came in, because he thought it a deed worthy of a free ingenuous man to kill Caius, and was ashamed of the reproaches he lay under from Caius, as though he were a coward; as also because he was himself in danger every day from his friendship with him, and the observance he paid him. These men proposed this attempt to all the rest that were concerned, who saw the injuries that were offered them, and were desirous that Caius's slaughter might succeed by their mutual assistance of one another, and they might themselves escape being killed by the taking off Caius; that perhaps they should gain their point; and that it would be a happy thing, if they should gain it, to approve themselves to so many excellent persons, as earnestly wished to be partakers with them in their design for the delivery of the city and of the government, even at the hazard of their own lives. But still Cherea was the most zealous of them all, both out of a desire of getting himself the greatest name, and also by reason of his access to Caius's presence with less danger, because he was tribune, and could therefore the more easily kill him.