His mother, like the rest of the women, was at this moment watching the battle from the house-top, and when she saw that her son was engaged in conflict with Pyrrhus she was filled with distress in view of the danger to him, and lifting up a tile with both her hands threw it at Pyrrhus. It fell upon his head below his helmet and crushed the vertebrae at the base of his neck, so that his sight was blurred and his hands dropped the reins. Then he sank down from his horse and fell near the tomb of Licymnius, unrecognised by most who saw him.
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/pyrrhus-e1015710 long-term consequence: Pyrrhus is slain by Zopyrus who sees him fall from his horse. This is mentioned in 34.3.
The armies fighting each other around him are not listed as third persons because it is clearly stated that nobody saw Pyrrhus falling.