Chapters 1+2 TKAM

In the novel “To kill a Mockingbird” By Harper Lee, the first chapter discusses a lot about a character named Author Radley, also known as Boo. I was wondering why the author would add this character into the novel? What does he symbolize? Is he supposed to resemble Harper Lee in any way? 

For instance, when Jem questioned Miss Stephanie about Boo, she told him “Boo drove the scissors into his parents leg, and pulled them out, wiped them on his pants and resumes his activities” (11). This passage really confused me because; the neighbour’s don’t know the whole story, this is true because he doesn't come out of his house, the only way to figure out the whole story is to ask the culprit. This also shows that the neighbour’s don’t show any empathy for Boo, which results in the solidarity of Boo. Another example, is when Radley was walked by the finches house, Calpurnia said “There goes the meanest man ever god blew breath into” (12).  This demonstrates what people see him as, most of the neighbours see him as a devil, or in other words, a person who is all bad.