The president most likely meant is Abraham Lincoln. He was shot at Ford’s Theatre, while the man who killed his assassin, John Wilkes Booth, was later found in a barn near Bowling Green, Virginia.

Why this gets mixed up

People often blur two different events:

  • Lincoln was the president who was assassinated.
  • Booth, Lincoln’s assassin, was cornered and shot in a barn afterward.

Other possible mix-up

If you meant a more recent shooting tied to a venue that looked like a farm or barn area, that could be Donald Trump at the Butler Farm Show in Pennsylvania, where he was injured in an assassination attempt.

If you want, I can give you a very short “who got shot where” list of U.S. presidents.