Why does Orestes kill Clytemnestra in Libation Bearers?

In Aeschylus’ Libation Bearers, Orestes returns home to avenge the murder of his father, Agamemnon, who was killed by his wife, Clytemnestra, and her lover, Aegisthus.12

While Orestes is driven by the desire to avenge his father, his decision to kill his mother is not made lightly. In the play, Orestes commits the act of matricide reluctantly, acting specifically at the bidding of the god Apollo. Following the murder, Orestes is unable to fully justify his actions; he becomes guilt-wracked and is pursued by the Furies, the incarnations of his mother's curse.12