Copy filefield image to different filefield field
I fixed it by running SQL on the database directly through phpmyadmin.
First I added the destination field to the content type.
Then, I went into phpmyadmin and ran this: (change your field names as appropriate.

INSERT field_data_field_image SELECT * FROM field_data_field_event_image;


and 

INSERT field_revision_field_image SELECT * FROM field_revision_field_event_image;


After it ran successfully, I went in and checked the content. All good. Then I was able to delete the old field. Problem solved! Thanks.