This isn’t a particularly shocking detail, given the fact that sexual violence against women is a very common theme in Greek mythology. He tried to seduce her, she didn’t want him, and he got pissed and raped her in Athena’s temple, purposefully choosing that location for extra insult to Athena. This version leaves out a really important detail that I only learned recently. Eventually Medusa’s head was given to Athena, who placed it on her shield. She was finally beheaded by the heroic Perseus, who used a mirror to avoid her gaze. Her head was considered a prize whoever could sever it would hold a weapon far more powerful than any other against their enemies.
Medusa retreated to a remote island where she began collecting stone statues of the men who tried to kill her.
Anyone who looked at Medusa from that point forward would turn to stone. She cursed Medusa, transforming her beautiful hair into a tangle of poisonous snakes. Athena was jealous, and when she found out that Medusa and Poseidon had broken her vow of chastity she went ballistic. She was a beautiful maiden with particularly lovely hair who committed herself to a chaste life in order to serve as a priestess to Athena. The version of Medusa’s myth that I knew growing up was probably pretty close to what most people know of her.