Did Harold Crick exist before the author began writing his story?

In the movie Stranger Than Fiction, Harold Crick is the main character in Karen Eiffel's book "Death and Taxes". She is shown narrating his world, however,

Which begs the question, did Harold exist before he was written about, and it was just chance that Karen Eiffel began writing about him and changing his life, or was it the case that she wrote him into existence in his entirety?