How do we know that Bob Ewell still remembers the humiliation he suffered at the trial?

One night, alone in his study, Judge Taylor finds the strange shadow of a prowler in his house and proceeds with his reading, but with a gun across his lap. Helen Robinson has been working on the property of Mr. Link Deas, but walks nearly a mile out of her way in order to avoid walking past the Ewell's house, because they "chunk" at her when she passes by. When Mr. Link Deas finds out, he approaches the Ewell house and yells to them, warning them not to bother Helen, or else he'll have them put in jail. The next day, Mr. Ewell follows Helen to work, "crooning foul words" the entire way, but Mr. Link Deas again threatens him with jail and he stops this behavior. Aunt Alexandra thinks that these events bode poorly for Atticus, as she is convinced that Ewell's threat after the trial carries more weight than Atticus is willing to believe.