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

[24] Now at this time came on the horse-races [Circensian games]; the view of which games was eagerly desired by the people of Rome, for they come with great alacrity into the hippodrome [circus] at such times, and petition their emperors, in great multitudes, for what they stand in need of; who usually did not think fit to deny them their requests, but readily and gratefully granted them. Accordingly, they most importunately desired that Caius would now ease them in their tributes, and abate somewhat of the rigor of their taxes imposed upon them; but he would not hear their petition; and when their clamors increased, he sent soldiers some one way and some another, and gave order that they should lay hold on those that made the clamors, and without any more ado bring them out, and put them to death. These were Caius's commands, and those who were commanded executed the same; and the number of those who were slain on this occasion was very great. Now the people saw this, and bore it so far, that they left off clamoring, because they saw with their own eyes that this petition to be relieved, as to the payment of their money, brought immediate death upon them. These things made Cherea more resolute to go on with his plot, in order to put an end to this barbarity of Caius against men. He then at several times thought to fall upon Caius, even as he was feasting; yet did he restrain himself by some considerations; not that he had any doubt on him about killing him, but as watching for a proper season, that the attempt might not be frustrated, but that he might give the blow so as might certainly gain his purpose.