What method does the author use in chapter 6 to build suspense?

There is some more childish efforts to see Boo Radley but this time things get serious.  Jem loses his pants in the gate. As they run, they hear a shotgun sound somewhere behind them. When they return, Mr. Radley is standing inside his gate, and Atticus is there with various neighbors. They hear that Mr. Radley was shooting at a "white Negro" in his backyard, and has another barrel waiting if he returns. It is the last day of Dill's summer with them but I am unsure exactly how much time has past.