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 a career milestone for Lee. Twenty years ago this month, his first feature film, “She’s Gotta Have It,” hit theaters to instant praise from critics.

Nearly all of Lee’s films have strong African-American themes and characters. Though filmmakers have always dabbled in racial topics, Lee, who is black, has been unique, steadfastly chipping away at the subject in ever more complex ways.

“He’s made a tremendous difference in the history of American cinema,” said Jacqueline Stewart, a film professor at Northwestern University in Chicago who teaches a class on Lee’s work. “Spike Lee’s films get people to talk about what race means and how race continues to function in our society.”

For years, Lee did that with an in-your-face approach – characters that yelled racial slurs at the screen, on-screen brawls between whites and blacks. Lee himself was often in front of the camera, playing a string of incendiary sidekick characters. He also often wrote, produced and directed his films, enlisting family members to contribute music, writing and acting.

But in recent years, he has stepped back. He did not write or appear on-screen in “Inside Man,” “She Hate Me” in 2004 or 2002’s “25th Hour.” Though he remains focused on black America, his approach has become quieter, less self-conscious.

“Levees” reflects that.

Using current and historical footage, music and more than 100 interviews, the film reminds viewers that although Katrina shattered the entire Gulf Coast, New Orleans and its mostly black residents got hit especially hard. Thousands fought to survive deadly floodwaters for days while federal help was slow in coming. Many are left today with a nearly ruined city and broken hearts.

Lee conducted each of the interviews, and viewers occasionally hear him asking questions, but he never steps in front of the camera. There is no narrator telling viewers New Orleans was abandoned, or this may have happened because most residents are black. There is no need.

“Let the people tell it, the witnesses,” said Lee, 49, during an interview this week. “People are giving testimonial, sharing all the rage and anger. What they’re doing is sharing their humanity with us.”

Nevins said the film is “a surrender of the ego of the maker to the people.”

Despite heavy media coverage of Katrina, the film pulls together the before, during and after of the storm in a way that manages to be agonizingly fresh.

One man tells of being forced to abandon his dead mother’s body in the city’s Superdome. He pinned a note with his phone number on her shroud.

The film, Lee said, is ultimately a plea to renew the city, where most of those forced out have not yet returned, tons of debris remains and there is no comprehensive rebuilding plan. “We want this film to spur action,” he said. “Things still aren’t right. People are still suffering.”