On the morning of Friday April 14, 1865, Booth learned that Lincoln would be attending at performance of Our American Cousin that night at Ford's Theater. Moving quickly, he summoned his remaining conspirators to a meeting in Powell's room at the Herndon House. He informed them that capturing the president would no longer be enough to save the Southern cause and, in a low whisper, began to outline a new plan which involved killing Lincoln, Vice President Andrew Johnson, and Secretary of State William Seward. While Booth planned to kill Lincoln himself, he assigned Atzerodt the task of killing Johnson, while Powell was to kill Seward. As Powell was unfamiliar with Washington, Herold was tasked with guiding him out of the city after the assassination had been completed. For their escape, the conspirators would use the network that had been set up for the kidnapping plot.
Booth informed his men that the attacks were to be carried out simultaneously around 10:00 PM to ensure maximum confusion. Around 9:00 PM, Booth rode through Baptist Alley at the rear of Ford's Theater. As a well known actor he had free run of the theater and was friends with most of the staff. Dismounting, he asked stagehand Ned Spangler to hold his horse as it was skittish and did not like to be tied. Busy with theater work, Spangler passed the horse a young boy known as "Peanut John" Burroughs. For the next hour, Booth drank in the adjacent Star Saloon. Around 10:00 PM, he entered Ford's Theater and made his way upstairs to the presidential box. Drawing a Deringer pistol, Booth entered and shot Lincoln in the back of the head. Pushing forward, he grappled with Lincoln's companion, Major Henry Rathbone, and slashed him with a knife. Climbing over the railing, Booth became tangled in a Treasury Guards' flag and dropped to the stage. In his diary, which was highly dramatized, Booth claimed to have broken his leg when he fell. Witnesses stated that Booth yelled something as he attempted to escape, but his exact words were not remembered. Tradition states that it was "Sic Semper Tyrannis" (Thus be ever to tyrants) in reference to the Virginia state motto. Striding purposefully across the stage, Booth exited the rear of the theater. Taking his horse from Peanut John, he fled down Baptist Alley.
In the theater, Lincoln's condition was assessed and it was decided to move him across the street to the Petersen boarding house. He died at 7:22 AM the following morning.