Hello. You did not say the text to which this question refers, which makes it impossible for this question to be answered accurately. However, I will try to help you in the best way possible.
To build up tension before the forest incident, the author can build a narration that imposes a totally unpredictable atmosphere and promotes a strong suspense in the reader. In this case, the author does not show any kind of foreshadowing, but only accumulates unpredictable, unthinkable and incalculable elements that make the reader understand that anything can happen at any time in history.
