Esther 3:15 (ESV)

15 The couriers went out hurriedly by order of the king, and the decree was issued in Susa the citadel. And the king and Haman sat down to drink, but the city of Susa was thrown into confusion.

The couriers were spurred on to spread the news with the utmost speed. Meanwhile (perhaps as they started with their Passover celebrations), the Jews in Susa discovered the news with horror. Not only they, but also the other inhabitants of Susa were thrown into confusion by the decree. This reaction forms a stark contrast with that of Ahasuerus and Haman, who coolly sat down to drink.