Tiberius on Caligula the Snake and Other Contextual Problems

It is my suggestion that Tiberius fled Rome because he interpreted the death of his pet snake as the warning of a threat to the life of one of his current favourites and intended successors, Caligula, rather than to his own life. Yet Suetonius, or perhaps the author of his immediate source, has torn Tiberius' words from their original context so that they appear to depict Caligula as the threat rather than the victim. The similarities between the accounts by Tacitus and Suetonius of the last days of Tiberius encourage the belief that they relied on the same main source for this period, or some edition of the same source at least.