Diogenes Laertius, Lives of the Eminent Philosophers 7.28
The death of Zeno the Stoic.
ἐτελεύτα δὴ οὕτως· ἐκ τῆς σχολῆς ἀπιὼν προσέπταισε καὶ τὸν δάκτυλον περιέρρηξε· παίσας δὲ τὴν γῆν τῇ χερί φησι τὸ ἐκ τῆς Νιόβης “ἔρχομαι· τι? μ’ αὔεις;” και παραχρῆμα ἐτελεύτησεν ἀποπνίξας ἑαυτόν.
He died in this way: as he was leaving the school he stumbled and broke his toe. He struck the ground with his hand, spoke the line from Niobe, ‘I am coming! Why do you call me?’, and immediately suffocated himself to death.