The story occurs in Phanias of Eresos

In Herakleia in Italy there was a beautiful boy called Hipparinos who came from a very good family. His lover, Antileon, tried everything but was wholly unable to win him round. He would often dash up to the boy, who was a regular at the gymnasia, declaring that he wanted him so much that he would endure any hardship, that whatever the boy told him to do, he would fail in nothing.

Now the boy asked him ironically to fetch the bugle from a certain rocky place that was kept under special guard by the Herakleian tyrant,[1] convinced that Antileon would never manage this feat.

But Antileon secretly approached the fort, lay in wait for the man who was guarding the bugle, and killed him. And when he came back to the boy, the mission accomplished, the boy became very fond of him and from that time onwards they loved each other dearly.

When the tyrant began to lust after the boy’s[2] beauty and was on the point of using force to abduct him, Antileon was outraged. He told the boy not to incur risks by a refusal; but he himself, when the tyrant was leaving his house one day, rushed up and assassinated him.[3]

This done, he fled and would have escaped had he not fallen in with a flock of sheep all tied together and been captured. So once the city had returned to its original constitution the Herakleiotes erected bronze statues to both men, and a law was enacted that no-one in the future was to drive bound sheep.

Ἱστορεῖ Φανίας ὁ Ἐρέσιος

[1] Ἐν δὲ τῇ Ἰταλῇ Ἡρακλείᾳ παιδὸς διαφόρου τὴν ὄψιν (Ἱππαρῖνος [ἦν] αὐτῷ ὄνομα) τῶν πάνυ δοκίμων Ἀντιλέων ἠράσθη· ὃς πολλὰ μηχανώμενος οὐδαμῇ δυνατὸς ἦν αὐτὸν ἁρμόσασθαι, περὶ δὲ γυμνάσια διατρίβοντι πολλὰ τῷ παιδὶ προσρυεὶς ἔφη τοσοῦτον αὐτοῦ πόθον ἔχειν ὥστε πάντα πόνον ἂν τλῆναι καὶ ὅ τι ἂν κελεύοι³, μηδενὸς αὐτὸν ἁμαρτήσεσθαι.

[2] ὁ δὲἄρα κατειρωνευόμενος προσέταξεν αὐτῷ ἀπό τινος ἐρυμνοῦ χωρίου, ὃ μάλιστα ἐφρουρεῖτο ὑπὸ τοῦ⁴ τῶν Ἡρακλεωτῶν τυράννου, τὸν κώδωνα κατακομίσαι, πειθόμενος μὴ ἄν ποτε τελέσειν αὐτὸν τόνδε τὸν ἄθλον.

[3] Ἀντιλέων δὲ κρύφα τὸ φρούριον ὑπελθὼν καὶ λοχήσας τὸν φύλακα τοῦ κώδωνος κατακαίνει· καὶ ἐπειδὴ ἀφίκετο πρὸς τὸ μειράκιον ἐπιτελέσας τὴν ὑπόσχεσιν, ἐν πολλῇ αὐτῷ εὐνοίᾳ ἐγένετο, καὶ ἐκ τοῦδε μάλιστα ἀλλήλους ἐφίλουν.

[4] ἐπεὶ δὲ ὁ τύραννος τῆς ὥρας ἐγλίχετο τοῦ παιδὸς καὶ οἷός τε ἦν αὐτὸν βίᾳ ἄγεσθαι, δυσανασχετήσας ὁ Ἀντιλέων ἐκείνῳ μὲν παρεκελεύσατο μὴ ἀντιλέγοντα κινδυνεύειν· αὐτὸς δὲ οἴκοθεν ἐξιόντα τὸν τύραννον προσδραμὼν ἀνεῖλεν.

[5] καὶ τοῦτο δράσας δρόμῳ ἵετο καὶ διέφυγεν ἄν, εἰ μὴ προβάτοις συνδεδεμένοις ἀμφιπεσὼν ἐχειρώθη. διὸ τῆς πόλεως εἰς τἀρχαῖον ἀποκαταστάσης, ἀμφοτέροις παρὰ τοῖς Ἡρακλεώταις ἐτέθησαν εἰκόνες χαλκαῖ, καὶ νόμος ἐγράφη, μηδένα ἐλαύνειν τοῦ λοιποῦ πρόβατα συνδεδεμένα.

Hipparinos the tyrant of Syracuse[4] fell in love with a very beautiful boy called Achaios. He used many inducements and diversions to persuade him to leave home and stay with him. Time went by, and word came of an enemy attack on one of the territories occupied by him: immediate action was needed. Hipparinos, on his way out, instructed the boy that if anyone should offer him violence inside the palace, then he was to kill him with the short sword he had given him.

Then, coming to blows with the enemy, he defeated them soundly, and afterwards turned to wine and carousing. Inflamed with drink and desire for the boy, he spurred his horse away to Syracuse; when he reached the house where he had told the boy to stay, he concealed his identity but adopted a Thessalian accent,[5] and declared he had killed Hipparinos. The boy was outraged and, it being dark, delivered Hipparinos a fatal wound. He lived on for three days after that, and died after absolving Achaios of the murder.

[1] Ἱππαρῖνος δὲ Συρακοσίων τύραννος εἰς ἐπιθυμίαν ἀφίκετο πάνυ καλοῦ παιδός (Ἀχαιὸς αὐτῷ ὄνομα). τοῦτον ἐξαλλάγμασι πολλοῖς ὑπαγόμενος πείθει τὴν οἰκίαν ἀπολιπόντα σὺν αὐτῷ μένειν. χρόνου δὲ προϊόντος, ὡς πολεμίων τις ἔφοδος προσηγγέλη πρός τι τῶν ὑπ᾿ ἐκείνου κατεχομένων χωρίων καὶ ἔδει κατὰ τάχος βοηθεῖν, ἐξορμῶν ὁ Ἱππαρῖνος παρεκελεύσατο τῷ παιδί, εἴ τις ἐντὸς τῆς αὐλῆς βιάζοιτο, κατακαίνειν αὐτὸν τῇ σπάθῃ ἣν ἐτύγχανεν αὐτῷ κεχαρισμένος.

[2] καὶ ἐπειδὴ συμβαλὼν τοῖς πολεμίοις κατὰ κράτος αὐτοὺς εἷλεν, ἐπὶ πολὺν οἶνον ἐτράπετο καὶ συνουσίαν. ἐκκαιόμενος δὲ ὑπὸ μέθης καὶ πόθου τοῦ παιδὸς ἀφίππευσεν εἰς τὰς Συρακούσας καὶ παραγενόμενος ἐπὶ τὴν οἰκίαν ἔνθα τῷ παιδὶ παρεκελεύσατο μένειν, ὃς μὲν ἦν οὐκ ἐδήλου, Θετταλίζων δὲ τῇ φωνῇ τὸν Ἱππαρῖνον ἔφησεν ἀπεκτονηκέναι. ὁ δὲ παῖς διαγανακτήσας σκότους ὄντος παίει καιρίαν τὸν Ἱππαρῖνον· ὁ δὲ τρεῖς ἡμέρας ἐπιβιοὺς καὶ τοῦ φόνου τὸν Ἀχαιὸν ἀπολύσας ἐτελεύτησεν.