From Hell Letter

Please note that the content of this book primarily consists of articles
available from Wikipedia or other free sources online. The "From Hell"
letter (or the "Lusk letter") is a letter posted in 1888 by a man who
claimed to be the serial killer known as Jack the Ripper. Though many
hundreds of letters claiming to be from the killer were posted at the
time of the Ripper murders, many researchers argue that the "From Hell"
letter is one of a handful of possibly authentic writings received from
the murderer.