Attacks ascribed to Jack the Ripper typically involved female prostitutes who lived and worked in the slums of the East End of London whose throats were cut prior to abdominal mutilations. The removal of internal organs from at least three of the victims led to proposals that their killer had some anatomical or surgical knowledge. Rumours that the murders were connected intensified in September and October 1888, and letters were received by media outlets and Scotland Yard from a writer or writers purporting to be the murderer. The name "Jack the Ripper" originated in a letter written by someone claiming to be the murderer that was disseminated in the media. The letter is widely believed to have been a hoax and may have been written by journalists in an attempt to heighten interest in the story and increase their newspapers' circulation. The "From Hell" letter received by George Lusk of the Whitechapel Vigilance Committee came with half of a preserved human kidney, purportedly taken from one of the victims. The public came increasingly to believe in a single serial killer known as "Jack the Ripper", mainly because of the extraordinarily brutal nature of the murders, and because of media treatment of the events.