Passage 1.16.2
ὡς δέ οἱ ταῦτα προκεχωρήκει καὶ μετʼ ὀλίγον τὰ Λυσιμάχου κατείργαστο, τὴν μὲν ἐν τῇ Ἀσίᾳ πᾶσαν ἀρχὴν παρέδωκεν Ἀντιόχῳ τῷ παιδί, αὐτὸς δὲ ἐς Μακεδονίαν ἠπείγετο. στρατιὰ μὲν καὶ Ἑλλήνων καὶ βαρβάρων ἦν παρὰ Σελεύκῳ· Πτολεμαῖος δὲ ἀδελφὸς μὲν Λυσάνδρας καὶ παρὰ Λυσιμάχου παρʼ αὐτὸν πεφευγώς, ἄλλως δὲ τολμῆσαι πρόχειρος καὶ διʼ αὐτὸ Κεραυνὸς καλούμενος, οὗτος ὁ Πτολεμαῖος, ὡς προσιὼν ὁ Σελεύκου στρατὸς ἐγένετο κατὰ Λυσιμάχειαν, λαθὼν Σέλευκον κτείνει, διαρπάσαι δὲ ἐπιτρέψας τὰ χρήματα τοῖς βασιλεῦσιν ἐβασίλευσε Μακεδονίας, ἐς ὃ Γαλάταις πρῶτος ὧν ἴσμεν βασιλέων ἀντιτάξασθαι τολμήσας ἀναιρεῖται ὑπὸ τῶν βαρβάρων· τὴν δὲ ἀρχὴν Ἀντίγονος ἀνεσώσατο ὁ Δημητρίου.
When these undertakings had progressed successfully for Seleucus, and shortly afterward he had also finished off Lysimachus's affairs, he transferred the entire rule of Asia to his son Antiochus, and hastened himself towards Macedonia. Seleucus had with him an army of both Greeks and barbarians. Now Ptolemy—brother of Lysandra, who had fled from Lysimachus to Seleucus, being naturally daring and therefore called "Ceraunus" (the Thunderbolt)—when Seleucus's army reached the vicinity of Lysimacheia, secretly slew Seleucus. After allowing the kings to plunder Seleucus's treasures, this same Ptolemy reigned over Macedonia, until he became the first king known to us to dare resistance against the Gauls, and he was slain by these barbarians. Afterward, Antigonus, the son of Demetrius, recovered the kingdom.