NEW YORK — Several weeks after Hurricane Katrina drowned New Orleans, HBO documentary executives were stumped. How to respond on film to something so monumental? "We were in a meeting one day and I said, `I guess we'll have to let Katrina go,'" said Sheila Nevins, president of HBO Documentary and Family. "Then, literally within the hour, Spike called. It was like, `Eureka!'" Spike Lee was quickly signed to chronicle the storm and its aftermath in New Orleans. The first half of Lee's heartbreaking film, "When the Levees Broke: A Requiem in Four Acts," debuts Monday. The four-hour documentary marks...