Why isn't the sherifff there to back up Atticus?

The sheriff, Heck Tate, isn't there to back up Atticus Finch during the tense scene in "To Kill a Mockingbird" because he is busy ensuring the safety of the town and dealing with the potential threats posed by the mob. Atticus stands alone to protect Tom Robinson, believing in the importance of moral integrity and justice. This moment underscores Atticus's commitment to doing what is right, even when he faces danger without immediate support. It highlights the themes of courage and individual responsibility in the face of social injustice.