The feeling of apprehension and suspense is created with the reference to Mr. Ewell targeting Atticus.
In this chapter, Tom Robinson has been killed and we see how Maycomb reacts. His wife collapses, and Mr. Underwood writes a scathing editorial in the paper about how it is a sin to kill cripples regardless of race. Mr. Ewell is the one that Scout is afraid of. She knows that he is aware that everyone in town, including the jury, is aware of Tom Robinson’s innocence. The only reason Atticus did not get a conviction was that it is impossible in that time to convict a black man on the word of a white woman. So Tom was convicted in a court of law, but the whispers of public opinion were different, and that was enough for Bob Ewell. He felt betrayed.
Miss Stephanie told Aunt Alexandra in Jem's presence ("Oh foot, he's old enough to listen.") that Mr. Ewell said it made one down and about two more to go. (Ch. 25)
Jem tells Scout not to worry about Bob Ewell, because he is only “hot gas.” However, this incident is enough foreshadowing to make the reader wonder. After all, we know that Bob Ewell is dangerous. Someone beat up Mayella. The reader sees the incident for what it is. Also, Jem warns Scout not to tell Atticus. If there wasn’t something to really be worried about, he would not say that. Therefore, Jem actually is scared. Bob Ewell is something to be concerned about.
As it turns out, Scout’s fears are not unfounded. First, Bob Ewell spits in Atticus’s face and accuses him of being a traitor. Then, he attacks his children. If Boo/Arthur Radley had not been there to protect them, Ewell might have injured or killed the kids.