David Mills, a former journalist who explored race relations and racial tensions as an Emmy-winning television writer for dramas like “NYPD Blue,” “The Wire” and “Homicide,” died on Tuesday in New Orleans on the set of a new show, “Treme.” He was 48 and had homes in Los Angeles and Silver Spring, Md.

The cause is thought to be a brain aneurysm, said David Simon, the creator of “Treme” and a longtime friend of Mr. Mills’s.

The show, which is set in New Orleans in the aftermath of Hurricane Katrina — the title is the name of a neighborhood, pronounced truh-MAY — is to have its premiere on HBO on April 11. Mr. Simon said Mr. Mills was the supervising writer-producer for a scene being shot at Cafe du Monde in the French Quarter and was sitting in a director’s chair when he suddenly slumped over. He was taken to Tulane Medical Center, where he died without regaining consciousness.

“He was talking to someone who turned away for a minute, and when he turned back, David was just, well, gone,” Mr. Simon said.

Both as a journalist — he worked for The Wall Street Journal, The Washington Times and The Washington Post — and as a television writer, Mr. Mills was most interested in the subject of race. He wrote about its manifestations in music, politics and American culture in general in a forthright style and with a voice that betrayed fascination but no ideology or identifiable bias.

A light-skinned black man whose racial identity was not always evident to those around him, he wrote white characters and black characters with equal zeal, as shown in episodes of “NYPD Blue” featuring the racially insensitive white police officer Andy Sipowicz (played by Dennis Franz) and the often seething black lieutenant Arthur Fancy (James McDaniel). Mr. Mills was able “to travel with great fluidity between worlds and communities,” Mr. Simon said.

Mr. Mills’s blog, which he wrote for the past five years, was called “Undercover Black Man.”

Mr. Mills shared two Emmy awards — one for outstanding mini-series, one for outstanding writing for a mini-series — for his work on “The Corner,” a six-episode drama about a year in the life of a neighborhood in inner-city Baltimore that was based on a book by Mr. Simon and Ed Burns and was shown on HBO in 2000. The relationship of Mr. Mills, Mr. Simon, who is white, and the show’s director, Charles Dutton, who is black, was the subject of an article in The New York Times in 2000, “Who Gets to Tell a Black Story?,” that was part of the paper’s series Pulitzer Prize-winning series “How Race Is Lived in America.”

Mr. Mills also wrote for Mr. Simon’s other notable dramas, “Homicide,” set in Baltimore; and “The Wire,” HBO’s taut prison series. His other credits included “E.R.,” NBC’s long-running hospital show, and “Kingpin,” a show he created about a drug trafficker that was canceled by NBC after six episodes in 2003.

David Eugene Mills was born in Washington and grew up in the northeast section of the city before a fire forced his family to move to Lanham, Md. He graduated from the University of Maryland at College Park, where he met Mr. Simon while the two worked for The Diamondback, the campus daily newspaper.

After college he worked for The Wall Street Journal in Chicago, but left after a year to return to Washington to write first for The Times and then The Post, where he covered race and popular culture. His interview with the rapper Sister Souljah after the Los Angeles riots of 1992 created headlines when an already incendiary quotation from her — “I mean, if black people kill black people every day, why not have a week and kill white people?” — was cited by an outraged presidential candidate, Bill Clinton.

The same year, Mr. Simon asked Mr. Mills for help in writing an episode of “Homicide,” which was being adapted from Mr. Simon’s nonfiction book about the Baltimore police department’s homicide unit. After the episode, which starred Robin Williams, was broadcast in 1994, Mr. Mills left The Post for Hollywood.

He worked briefly as a story editor for the David Kelley series “Picket Fences,” but his big break came when he read an interview with David Milch, the lead writer of “NYPD Blue,” who said that black writers had a hard time writing for mainstream commercial television. Mr. Mills wrote an arch note to Mr. Milch, who hired him.

For his work on the show, he was nominated twice for Emmys.

Mr. Mills is survived by a brother, Franklin Mills, of Washington, and two sisters, Blanche Carroll, of Peoria, Ariz., and Gloria Johnson, of Charlotte, N.C.