Titus Livius (Livy), The History of Rome, Book 1
D. Spillan, A.M., M.D., Ed.

40. About the thirty-eighth year of Tarquin's reign, Servius Tullius was in the highest esteem, not only with the king, but also with the senate and people. [2] At this time the two sons of Ancus, though they had before that always considered it the highest indignity that they had been deprived of their father's crown by the treachery of their guardian, that a [p. 54]stranger should be king of Rome, who was not only not of a civic, but not even of an Italian family, yet now felt their indignation rise to a still higher pitch at the notion that the crown would not only not revert to them after Tarquin, but would descend even lower to a slave, so that in the same state about the hundredth year¹ after Romulus, descended from a deity, and a deity himself, occupied the throne as long as he lived, a slave, and one born of a slave, should now possess it. [3] That it would be a disgrace both common to the Roman name, and more especially to their family, if, whilst there was male issue of king Ancus still living, the sovereignty of Rome should be accessible not only to strangers, but even to slaves. They determine therefore to prevent that disgrace by the sword. [4] But both resentment for the injury done to them incensed them more against Tarquin himself, than against Servius; and (the consideration) that a king was likely to prove a more severe avenger of the murder, if he should survive, than a private person; and moreover, in case of Servius being put to death, whatever other person he might select as his son-in-law,² it seemed likely that he would adopt as his successor on the throne.³ For these reasons the [5] plot is laid against [p. 55]the king himself. Two of the most ferocious of the shepherds being selected for the daring deed, with the rustic implements to which each had been accustomed, by conducting themselves in as violent a manner as possible in the porch of the palace, under pretence of a quarrel, draw the attention of all the king's attendants to themselves; then, when both appealed to the king, and their clamour reached even the interior of the palace, they are [6] called in and proceed before the king. At first both bawled aloud, and vied in interrupting each other by their clamour, until being restrained by the lictor, and commanded to speak in turns, they at length cease railing. According to [7] concert, one begins to state the matter. When the king, attentive to him, had turned himself quite that way, the other, raising up his axe, struck it into his head, and leaving the weapon in the wound, they both rush out of the house.