The brilliance of "The Sting" lies in its multi-layered deception, which cons both the antagonist and the audience. The central twist of the film is that the entire final act is a meticulously staged performance. Throughout the movie, Johnny Hooker is seemingly being pressured by FBI Agent Polk to betray Henry Gondorff. This creates immense tension, leading the audience to believe that Hooker's loyalty is genuinely in question.
In the climactic scene, after Lonnegan has placed his massive, un-winnable bet, the FBI storms the betting parlor. In the chaos, Gondorff, appearing to be betrayed, shoots Hooker. Agent Polk then immediately shoots Gondorff. For a moment, it seems both heroes are dead, a tragic end to their elaborate plan. Lt. Snyder quickly escorts a stunned Lonnegan away from the crime scene to avoid implication, leaving Lonnegan without his half-million dollars but believing his enemies are dead.
However, once Lonnegan is gone, Hooker and Gondorff rise, unharmed, to the cheers of the entire crew. It is revealed that the "FBI agents" were actually part of Gondorff's team of con men, and the shootings were faked with blanks and fake blood. The entire FBI pressure plot was the final layer of the con—a "con on the con" designed to ensure Lonnegan would be so flustered by the raid and the apparent murders that he would abandon his money without ever realizing he'd been swindled. The ultimate goal—to keep Lonnegan's con after taking his money—is achieved perfectly, as he leaves convinced he witnessed a federal bust gone wrong, not a masterful sting.