Bust of the emperor Gaius Caligula, ruled 37- 41 CE. (Getty Villa Museum). There are few surviving sources about the reign of Emperor Caligula, although he is described as a noble and moderate ruler during the first six months of his reign. After this, the sources focus upon his cruelty, sadism, extravagance, and sexual perversity, presenting him as an insane tyrant. In early 41 CE, Caligula was assassinated as a result of a conspiracy by officers of the Praetorian Guard, senators, and courtiers.