Lincoln vs Booth mano a mano

[LincolnMan]

The Kundhardt's speculated that Lincoln caught a glimpse of someone behind him and turned his head sharply to the left. They stated this explained the diagonal track of the ball.

Yes, I heard that too. I don't know where I read it, but I seem to recall that General Burnside caught Lincoln's attention. The General was either coming to his seat or leaving-and Lincoln turned his head noticing him.