Final answer:
In 'To Kill a Mockingbird', Mr. Ewell saw his daughter Mayella interacting with a black man, which angered him due to societal norms.
Step-by-step explanation:
In the novel 'To Kill a Mockingbird', when Mr. Ewell arrived on the scene, he saw his daughter, Mayella, through the window, interacting with a black man, Tom Robinson. This infuriated him because it challenged the racial hierarchy and social norms of the time, which dictated that interracial relationships were taboo. The incident ultimately led to the false accusation and wrongful conviction of Tom Robinson.