'Butch Cassidy And The Sundance Kid:' Why That Ending?

Left: The famous final image from 'Butch Cassidy And The Sundance Kid.' Right: Robert Redford as Harry 'Sundance Kid' Longabaugh. Source: IMDB

Butch Cassidy And The Sundance Kid's ending, a freeze-frame of our outlaw heroes right before they charge half of the Bolivian army, is sudden and might even make the film seem incomplete. Based on historical facts and the overwhelming odds, we can assume that this "blaze of glory" ends in the violent deaths of Butch and Sundance, played by Paul Newman and Robert Redford. But why did director George Roy Hill choose not to show us the shootout? It's one of the most memorable scenes in '60s cinema, perhaps because it isn't really a "scene" at all. It's a still image, accompanied by the shouts of the Bolivian soldiers and the sound of huge volleys of gunfire.