“John Wilkes Booth, to Lewis Powell after Lincoln's last public address (11 April 1865), as quoted in Steers, Edward (2002). Blood on the Moon. Lexington, Ky.: University Press of Kentucky. , p. 91. Also mentioned in Swanson, James. Manhunt: The 12-Day Chase for Lincoln's Killer. Harper Collins, 2006.”

Source: Wikiquote