Do what the Axe-Man says and nobody will get hurt

"Esteemed Mortal:

They have never caught me and they never will. They have never seen me, for I am invisible, even as the ether that surrounds your earth. I am not a human being, but a spirit and a fell demon from the hottest hell. I am what you Orleanians and your foolish police call the Axeman. When I see fit, I shall come again and claim other victims. I alone know who they shall be. I shall leave no clue except my bloody axe, besmeared with the blood and brains of him whom I have sent below to keep me company.
If you wish you may tell the police not to rile me. Of course I am a reasonable spirit. I take no offense at the way they have conducted their investigation in the past. In fact, they have been so utterly stupid as to amuse not only me but His Satanic Majesty, Francis Josef, etc. But tell them to beware. Let them not try to discover what I am, for it were better that they were never born than to incur the wrath of the Axeman. I don't think there is any need of such a warning, for I feel sure the police will always dodge me, as they have in the past. They are wise and know how to keep away from all harm.

Undoubtedly, you Orleanians think of me as a most horrible murderer, which I am, but I could be much worse if I wanted to. If I wished, I could pay a visit to your city every night. At will I could slay thousands of your best citizens, for I am in close relationship to the Angel of Death. Now, to be exact, at 12:15 (earthly time) on next Tuesday night, I am going to visit New Orleans again. In my infinite mercy, I am going to make a proposition to you people. Here it is: I am very fond of jazz music, and I swear by all the devils in the nether regions that every person shall be spared in whose home a jazz band is in full swing at the time I have mentioned. If everyone has a jazz band going, well, then, so much the better for you people. One thing is certain and that is that some of those people who do not jazz it on Tuesday night (if there be any) will get the axe.

Well, as I am cold and crave the warmth of my native Tartarus, and as it is about time that I leave your earthly home, I will cease my discourse. Hoping that thou wilt publish this, and that it may go well with thee, I have been, am and will be the worst spirit that ever existed either in fact or realm of fantasy.
The Axeman"

- A letter printed by the Times-Picayune on March 14th, 1919

I trust you can infer the rule on your own. Posts of my own creation will come soon when I am not jazzing it.