Lt. John Bolton was assigned to Ford’s Theatre to check officers’ passes on the evening of April 14. When he finished work, Bolton took a seat to enjoy the play.
He had seen John Wilkes Booth pass in and out several times while he was standing at the door examining passes, but he noticed nothing peculiar about the actor’s face or his actions. At least not until he heard a shot during the play’s third act.
Bolton saw a man lower himself by his left hand from the plush cushioned railing in front of the presidential box, but he thought it was part of the play. He said everyone sat still when Booth shouted, “Sic semper tyrannis!” and crossed the stage.
He said the audience’s first inkling that something was awry came when Bill Ferguson, who ran a saloon next door to the theater, rose from his orchestra seat and pointed to the presidential box shouting, “My God. The president’s shot!”
Actually Ferguson was sitting in the front row of the dress circle. He secured a seat early in the afternoon after one of the Ford’s tipped him off that the president would be attending that night’s performance. Ferguson wanted to see the president more than he wanted to see the play, so he booked a seat on the same level as the presidential box and brought his binoculars.
Source: We Saw Lincoln Shot: One Hundred Eyewitness Accounts by Timothy S. Good