From Wikipedia:

He was king of the Molossians, He was one of the strongest opponents of early Rome, and had been regarded as one of the greatest generals of antiquity. Several of his victorious battles caused him unacceptably heavy losses, from which the phrase "Pyrrhic victory" was coined.

...Pyrrhus was trapped. While he was fighting an Argive soldier, the soldier's old mother, who was watching from a rooftop, threw a tile which knocked him from his horse and broke part of his spine, paralyzing him. Whether he was alive or not after the blow is unknown, but his death was assured when a Macedonian soldier named Zopyrus, though frightened by the look on the face of the unconscious king, hesitantly and ineptly beheaded his motionless body.