Have a history teacher explain this----- if they can?

[Gumby]

Wasn't John F. Kennedy shot by Lee Harvey Oswald from the grassy noll

No. Oswald was in the book depository but there is strong conjecture that a second gunman fired the fatal head shot from behind a fence at the rear of the 'grassy noll'.

[Gingermick]

Norman Mailer wrote a very interesting book on Oswald.

The grassy knoll; Conspiracy theorists draw from the same well as the original post.
They take a conclusion and try to find evidence to support it, rather than accumulate evidence, then come to a conclusion.
A bit like jnr Bush as well.