This week marks the 150th anniversary of one of the most pivotal and dark moments in American history.

On April 14, 1865, John Wilkes Booth shot President Abraham Lincoln at Ford’s Theatre in Washington. Lincoln died nine hours later on the morning of April 15.

Lincoln arrived 15 to 20 minutes late to the theater the night he was shot, Lincoln expert Harold Holzer said.

“So word seems to pass through the audience that the president has arrived,” Holzer told WCBS 880’s Rich Lamb. “The actors see him. They stop the play. People stand up and start applauding, and by the time he reached the box, the band is playing ‘Hail to the Chief’ and people are throwing their hats in the air. So his last reception by the public was extrarodinary.”

The assassination occurred just five days after the Civil War had ended.

“And there was a guard, and the guard was convinced that since the war was over and everybody was in a great mood, after intermission he could just go to the local tavern and have a drink,” Holzer said.

A White House messenger was sitting outside the theater door leading to the president’s box. Booth, a well-known actor, showed the messenger his card and was allowed to go in, Holzer said.