Complex sentence: The story was mistaken for a factual account by many correspondents to the newspaper after its publication, and it is only after this date that other written references to a massacre at the cliffs of Waterloo Bay begin to emerge.
Split into simpler sentences: The story was mistaken for a factual account by many readers as indicated by correspondece with the newspaper after publishing. It is only after this date that other written references to a massacre at the cliffs of Waterloo Bay began to emerge.