But Demetrius, taking advantage of his opportunity, got beforehand with the young prince and slew him, and was proclaimed king of Macedonia.
Edition :
Plutarch Lives IX: Demetrius and Antony, Pyrrhus and Caius Marius, Ed. Jeffrey Henderson, trans. Bernadotte Perrin (The Loeb Classical Library 101), Harvard University Press: Cambridge/MA - London 1968 (first ed. 1920).
Remark :
date: The date is taken from the New Pauly. http://referenceworks.brillonline.com/entries/brill-s-new-pauly/demetrius-e314200 original citation: τὸ μειράκιον refers to Alexander, son of Cassander. He is mentioned earlier in the paragraph.