murder of one's master
Refers to the act of killing one's own master or lord, often in a historical or feudal context.
Murdering one's master was considered the greatest shame for a samurai.
murderer of one's master
Refers to the person who kills their own master or lord.
He became a fugitive as the murderer of his master.
Compound of 主 (しゅう, 'master') and 殺し (ごろし, 'killing'), from the verb 殺す (ころす).