John Wilkes Booth
That afternoon, Booth made a hole in a wall at the theater so he could see the President and his guests in their balcony room.  There were no guards protecting the balcony room.  During the play, Booth quietly entered the room. He knew that at 10:15 pm, the audience would laugh at a line in the play.  When the laughter began, Booth fired a pistol at point-blank range into the back of Lincoln's head. Booth escaped by jumping from the balcony onto the stage, where he shouted the triumphant line;Sic semper tyrannis  (‘Thus always to tyrants’)  to the audience. When he escaped from the box, he broke his leg during the jump, but escaped out the back door and onto his horse.