John and Henry are walking together in the park. Someone suddenly jumps out from behind a tree and then shoots John with a pistol.

Henry was not hit and he rushes John to the hospital. When John dies on the operating table, Henry dies soon after, even though no one had told Henry that John had died.

Why?

(note in these riddles, you can ask yes/no type questions for which I will provide answers to help you figure them out).