"Prince Xiao, or should I call you King of Hell?

Although this is just a guess, I believe it's quite close to the truth.

Upon reading this, King Xiao, please do not act rashly. Don't be in a hurry to kill me, or else nearly seventy percent of the citizens in the Imperial City will accompany me to the grave.

After reading this letter, please come to the Empress and Prince's Love-Filled Sunshine Welfare Institute, located at the east of the Imperial City, for a meeting.