“How to kill a mockingbird”, Harper Lee’s only published book contains a character based on his childhood friend who himself was a prolific writer. Who is this writer?

Truman Capote was Harper Lee's childhood friend and neighbor in Monroeville, Alabama. He became a renowned author of works like 'In Cold Blood' and 'Breakfast at Tiffany's'. The bond between Lee and Capote is well-documented, and he inspired the character Dill in 'To Kill a Mockingbird'. Note: the book title in the question is incorrectly written as 'How to kill a mockingbird' instead of 'To Kill a Mockingbird'.