Bob Ewell was not satisfied with Tom Robinson's guilty verdict, and he made threats to get even with Atticus. Bob apparently sought revenge against two others who were involved in the case. One night while Judge John Taylor was reading in his study, he heard noises outside. When he went to his back porch to investigate, he
... found the screen door swinging open. A shadow on the corner of the house caught his eye, and that was all he saw of his visitor.
Earlier in the story, Taylor (and readers) may have guessed that the shadow belonged to Boo Radley, who was rumored to often explore the neighborhood at night. However, Scout's narration suggests that the prowler was not Boo, but Bob.
Bob then turned his attentions to the daylight stalking of Helen Robinson, Tom's widow. Helen had resorted to walking "nearly a mile out of her way to avoid the Ewells," since Bob had "chunked at her"--throwing objects--as she passed by his house. A warning from Link Deas, Helen's boss, had no effect on Bob, who resorted to following Helen and cursing at her, "crooning foul words... (in) a soft voice." When Deas threatened to report Bob to the sheriff, Ewell bothered Helen no more.
Bob had already
... acquired and lost a job in a matter of days, and probably made himself unique in the annals of the nineteen-thirties: he was the only man I ever heard of who was fired from the WPA for laziness.
Bob had managed to obtain a government-subsidized job, but he didn't hold it long, and he blamed Atticus for " 'getting' his job."