By “Shushan the palace (or the fort),” is probably meant the whole of the upper town, which occupied an area of more than 100 acres, and contained many residences besides the actual palace. The Jews would not have ventured to shed blood within the palace-precincts.
Related Commentaries of Esther 9:6
Esther 9:6
6 And in Shushan the palace the Jews slew and destroyed five hundred men.