SUETONIUS, Life of Caligula
[II] Obiit autem, ut opinio fuit, fraude Tiberi, ministerio et opera Cn. Pisonis, qui sub idem tempus Syriae praepositus, nec dissimulans offendendum sibi aut patrem aut filium, quasi plane ita necesse esset, etiam aegrum Germanicum grauissimis uerborum ac rerum acerbitatibus nullo adhibito modo adfecit; propter quae, ut Romam rediit, paene discerptus a populo, a senatu capitis damnatus est.
2. Now the belief was that he met his death through the wiles of Tiberius, aided and abetted by Gnaeus Piso. This man had been made governor of Syria at about that time, and realizing that he must give offence either to the father or the son, as if there were no alternative, he never ceased to show the bitterest enmity towards Germanicus in word and deed, even after the latter fell ill. In consequence Piso narrowly escaped being torn to pieces by the people on his return to Rome, and was condemned to death by the senate.