In addition to Clara Diaz Sanchez' answer, I'd like to reveal some of the complexity of the Greek Myths around this subject, where there are many variations and overlaps between different mythological events and figures. There are actually multiple myths and myth-variants where a hero, king, or god is killed with a discus. According to Robert Graves, there was originally an icon depicting the sacrifice of the sacred king by his successor using a holy sun-disk (axe), after ruling for his allotted time (a season, 7 years, etc.). However, this icon was later reinterpreted by the ancient Greeks into various myths of death-by-discus.
Phocus’s death by the discus, like that of Acrisius (see 72. p), seems to be a misinterpretation of an icon which showed the end of the seal-king’s reign – the flying discus being a sun-disk; as the myth makes plain, the sacrificial weapon was an axe. Several heroes besides Achilles were killed by a heel wound, and not only in Greek but in Egyptian, Celtic, Lydian, Indian, and Norse mythology (see 90. 8 and 92. 10).
The myth of Antiope, Haemon, and the shepherds seems to have been deduced from the same icon as those of Arne (see 43. d) and Alope (see 49. a). We are denied the expected end of the story: that he killed his grandfather Creon with a discus (see 73. p).
The myth of Hyacinthus, which seems at first sight no more than a sentimental fable told to explain the mark on the Greek hyacinth (see 165. j and 2) concerns the Cretan Flower-hero Hyacinthus (see 159. 4), also apparently called Narcissus (see 85. 2), whose worship was introduced into Mycenaean Greece, and who named the later summer month of Hyacinthius in Crete, Rhodes, Cos, Thera, and at Sparta. Dorian Apollo usurped Hyacinthus’s name at Tarentum, where he had a hero tomb (Polybius: viii. 30); and at Amyclae, a Mycenaean city, another ‘tomb of Hyacinthus’ became the foundation of Apollo’s throne. Apollo was an immortal by this time, Hyacinthus reigned only for a season: his death by a discus recalls that of his nephew Acrisius (see 73. 3).
However, a storm arose and, while Acrisius’s ship was still hauled
up on the beach, weather-bound, Polydectes died. During his funeral games, Perseus threw a discus which accidentally struck Acrisius on the head and killed him. Perseus then sailed to Argos and claimed the throne, but found that Proetus had usurped it, and therefore turned him into stone; thus he now reigned over the whole of Argolis, until Megapenthes avenged his father’s death by murdering him.
One day Aeacus sent for Phocus, perhaps intending to bequeath him the island kingdom; but, encouraged by their mother, Telamon and Peleus plotted to kill him on his return. They challenged Phocus to a fivefold athletic contest, and whether it was Telamon who felled him, as if accidentally, by throwing a stone discus at his head, and Peleus who then despatched him with an axe, or whether it was the other way about, has been much disputed ever since. In either case, Telamon and Peleus were equally guilty of fratricide, and together hid the body in a wood, where Aeacus found it.
This is a theme that shows up in Grave's exegeses of the Greek Myths again and again: That originally these rituals and myths were concerned mainly with showing the ritual sacrifice of the sacred king, usually either by his successor or a priestess—or that they showed the sacrifice of a surrogate so that the king could continue to rule1—but that the (less) ancient Greeks misinterpreted many of the religious icons, vases, etc. depicting these rituals into new variations of the myths, in a time when human-sacrifice was no longer extant. Whether there's as much evidence for this interpretation as Graves claims is another question. That said, I highly recommend his Greek Myths, where he seems to have painstakingly tracked down and included basically every variation of every myth, and provided detailed and insightful interpretations of them.
1.
The burning of Thetis’s sons was common practice: the yearly sacrifice of boy surrogates for the sacred king (see 24. 10 and 156. 2). At the close of the eighth year the king himself died (see 91. 4 and 109. 3). A parallel in the Indian Mahabharata is the drowning by the Ganges-goddess of her seven sons by the God Krishna. He saves the last, Bhishma; then she deserts him. Actor’s division of his kingdom into three parts is paralleled in the myth of Proetus (see 72. h): the sacred king, instead of letting himself be sacrificed when his reign was due to end, retained one part of his kingdom, and bequeathed the remainder to his successors. Subsequent kings insisted on a lifetime tenure of sovereignty.
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