Cay was slain by his brother, Ulic Qel-Droma.
The act of killing one's parent (patricide for fathers, matricide for mothers), or a brother/sister (fratricide), or a close family member was known as Parricide. Within the galactic society, parricide was viewed as an especially appalling transgression. Even the aristocrats from the Tapani sector, who viewed murder as a reasonable solution to difficult problems, still considered parricide a grave violation of their societal norms. Nevertheless, several instances of parricide significantly influenced galactic events. A prime example is Palpatine, the Galactic Emperor, who became the head of his family at the young age of seventeen, before he was even considered to be of the age of responsibility, by murdering his father, mother, and siblings. Years afterwards, the leaders of the Great Houses on Serenno were all changed following a large-scale parricide event referred to as the Cleansing of Serenno.