Final answer:
In the movie 'Where the Crawdads Sing,' Kya is revealed to have killed Chase Andrews, with the truth being confirmed posthumously through her poetry book.
Step-by-step explanation:
In the movie Where the Crawdads Sing, the mystery of who killed Chase Andrews is a central plot element. Throughout the film, Kya, the main character, is accused of the murder. However, it is revealed towards the end that Kya indeed was responsible, and she left behind a hidden shell necklace at the scene as an intentional clue. In a shocking twist, it is revealed through a secret poetry book after her death that Kya committed the crime, thus ending the suspense for the audience.