It was during Cumanus' reign that troubles between the empire and the
Jewish nation began, events that lead to the first of two Jewish revolts
against the empire, which the empire eventually won, would eventually
result in the destruction of the Second Temple in A.D. 70.
During the Passover feast one year, one of Cumanus' soldiers dropped his pants and exposed his genetalia to the people who were celebrating in the Temple area. This lewd act was considered an affront to God. The people rose up in rebellion at the act, and the army then put on its armor and as it was walking through the streets 10,000 or 20,000 (Josephus cites both figures) of the Jews were killed as they trampled over one another in an effort to escape the soldiers.
After this, some of the people who were running away from the above mob scene came upon a tax-collector or some other Roman official named Stephen who was travelling along the public road. In their enraged state, they robbed him of the furniture he was carrying. Cumanus, when he found out about this, sent the army to counter-rob the surrounding towns. A soldier, in carrying out these orders, found a scroll with the Mosaic laws written on it, and publicly ripped it up, while shouting anti-Mosaic epithets. The Jews who saw this went to Cumanus, and told him that he would have to make things right with God, not just the people who had owned the scroll. Thus, to avoid further trouble, Cumanus had the soldier who had ripped up the Mosaic law beheaded.
The incident that ended Cumanus' career in Judaea was a rather convoluted affair that involved a conflict between the Jews and the Samaritans, bribery, and death. To try to resolve the conflict, the Legate of Syria, Ummidius Quadratus sent Cumanus and some of the leading Samaritans to Rome to answer before Claudius Caesar himself. Caesar, being predisposed, Josephus writes, on the side of the Jews by his Jewish friend Agrippa Junior and his wife Agrippina, banished Cumanus and had another official, Celer the Tribune, publically drawn through the streets of Jerusalem and then killed. Being a Roman official during the reign of Cumanus was dangerous to one's health.
Ancient sources: Antiquities 20.5.2-20.6.3; War 2.12.1-3, 2.12.5-7; Annals 12.54.
[12.54] Not equally moderate was his brother, surnamed Felix, who had for some time been governor of Judaea, and thought that he could do any evil act with impunity, backed up as he was by such power. It is true that the Jews had shown symptoms of commotion in a seditious outbreak, and when they had heard of the assassination of Caius, there was no hearty submission, as a fear still lingered that any of the emperors might impose the same orders. Felix meanwhile, by ill-timed remedies, stimulated disloyal acts; while he had, as a rival in the worst wickedness, Ventidius Cumanus, who held a part of the province, which was so divided that Galilea was governed by Cumanus, Samaria by Felix. The two peoples had long been at feud, and now less than ever restrained their enmity, from contempt of their rulers. And accordingly they plundered each other, letting loose bands of robbers, forming ambuscades, and occasionally fighting battles, and carrying the spoil and booty to the two procurators, who at first rejoiced at all this, but, as the mischief grew, they interposed with an armed force, which was cut to pieces. The flame of war would have spread through the province, but it was saved by Quadratus, governor of Syria. In dealing with the Jews, who had been daring enough to slay our soldiers, there was little hesitation about their being capitally punished. Some delay indeed was occasioned by Cumanus and Felix; for Claudius on hearing the causes of the rebellion had given authority for deciding also the case of these procurators. Quadratus, however, exhibited Felix as one of the judges, admitting him to the bench with the view of cowing the ardour of the prosecutors. And so Cumanus was condemned for the crimes which the two had committed, and tranquillity was restored to the province.The Complete Works of Tacitus, 1942 Translated by Alfred John Church and William Jackson Brodribb