 As a famous and popular actor who had frequently performed at Ford 's Theatre , and who was well known to its owner , John T. Ford , Booth had free access to all parts of the theater , even having his mail sent there . By boring a spyhole into the door of the presidential box earlier that day , the assassin could check that his intended victim had made it to the play and observe the box 's occupants . That evening , at around 10 p.m. , as the play progressed , John Wilkes Booth slipped into Lincoln 's box and shot him in the back of the head with a .41 caliber Deringer . Booth 's escape was almost thwarted by Major Henry Rathbone , who was present in the Presidential box with Mrs. Mary Todd Lincoln . Booth stabbed Rathbone when the startled officer lunged at him . Rathbone 's fiancée , Clara Harris , who was also present in the box , was unhurt . 
