Hoe does Lee create suspense leading up to the confrontation at the jailhouse?

Scout notices a group of men on their yard. She says that, "In Maycomb, grown men stood outside in the front yard for only two reasons: death and politics." This is a bad omen and Heck Tate has come to warn Atticus that something is up and he feels "uneasy" about Tom Robinson's move to the county jail. The suspense intensifies as Atticus takes his lamp to the courthouse. The mob shows up and the climax of the chapter takes place.