Sicarii, Sicarii

Some of their murders were met with severe retaliation by the Romans on the entire Jewish population of the country. On some occasions, they could be bribed to spare their intended victims. If the narrative of Barabbas is not an invention to create a parable, even convicted Sicarii were occasionally released on promising to spare their opponents, though there is no evidence for this practice outside the Gospels, which are largely in accord on this point. Once, Josephus relates, after kidnapping the secretary of Eleazar, governor of the Temple precincts, they agreed to release him in exchange for ten of their captured comrades.

One of many recent articles: http://www.ynetnews.com/articles/0,7340,L-3298583,00.html Sicarii had obvious parallels to a much later phenomenon, the medieval Hashshashin , Muslim fanatics whose talent for murders inspired the term assassin . The assassins, like the Sicarii, were notoriously willing to butcher coreligionists who didn't back their policies. Like the fanatical Masada holdouts, the Assassins built mountain fortresses in desolate areas to defend themselves against military enemies. They also used the dagger almost exclusively to carry out assassinations.

Source: Wikipedia > Sicarii