When, therefore, Cassander saw Demades after his arrival, he arrested him, and first slaughtered his son, whom he had brought so near that the folds of his father's robe caught the blood of his murder and were filled with it, and then, after heaping much insult and abuse upon him for his ingratitude and treachery, slew the father too.
Edition :
Plutarch's Lives VIII: Sertorius and Eumenes, Phocion and Cato the Younger, ed. Bernadotte Perrin, Harvard University Press: Cambridge/MA - William Heinemann Ltd.: London 1919 (The Loeb Classical Library 100).
Notes :
Cassander had found letters by Demades that were insulting to the memory of his father.