Stephen M. Archer, "Booth, John Wilkes," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-01210.html.
Booth meanwhile had entered Ford's Theatre at about ten o'clock, moving across the rear of the balcony to the president's box. Waiting for the audience's laughter to cover the report of his derringer, Booth entered the box and fired a single .44-calibre bullet at point-blank range into the back of Lincoln's head. He shouted "Sic semper tyrannis! The South is avenged!" according to some, slashing with a dagger at Major Henry Rathbone, who tried to restrain him. Booth then leaped the twelve feet from the presidential box onto the stage, breaking his left leg. He escaped from the theater to a waiting horse, and, accompanied by [David] Herold, fled Washington. They stopped at the home of Dr. Samuel A. Mudd in Bryantown, Maryland, to have Booth's leg set, then hid in neighboring woods for six days while federal troops vainly searched for them.