Sunday marks the fourth anniversary of the terrorist attacks on New York's World Trade Center and the Pentagon.

Several new programs, all airing on Sunday, explore various aspects of the tragedy:

History Channel offers "Osama's Hideouts" at 7 p.m., tracking the movements of Osama bin Laden from Pakistan through other locations. "The Man Who Predicted 9/11" follows at 8 p.m., spotlighting Morgan Stanley Dean Witter's director of security, Rick Rescorla. He predicted the attack and led hundreds to safety out of the World Trade Center's South Tower before he died in its collapse.

"Grounded on 9/11" at 9 p.m. on History Channel describes how the FAA ordered all aircraft out of the skies after two commercial jetliners were deliberately crashed into the World Trade Center.

"For the Love of Their Brother" (10:30 p.m., WQED) on PBS tells the story of New York firefighter Stephen Siller, who had finished his shift and was en route home to Staten Island when he learned a plane had struck the World Trade Center. With the Battery Tunnel closed to traffic, Siller ran toward the site to help, wearing 75 pounds of fire gear. He perished in the collapse of the towers.

To honor Siller's memory, his six siblings established the annual "Tunnel to Towers Run" for charity, which retraces the firefighter's final steps.

Several rebroadcasts air Sunday:

"The Anatomy of September 11th" at 1:30 p.m. on A&E offers a detailed account of the final 102 minutes before the World Trade Center's collapse, from the viewpoint of reporters and others present.

"World Trade Center: Rise and Fall of an American Icon" at 4 p.m. on History Channel explores the background of the physical and symbolic stature of the twin towers in the New York skyline.

"Inside 9/11," a two-part, four hour documentary that looks at the terrorist attacks and the events leading to them, is rebroadcast at 1 p.m. on National Geographic Channel. (Kathy Blumenstock, The Washington Post)

NEW CHIEF AT NBC NEWS

Steve Capus was named acting president of NBC News on Tuesday, replacing embattled Neal Shapiro, who resigned effective Friday.

Shapiro, news division chief since 2001 and a 12-year NBC veteran, had been asking off the presidency since May. No word whether he'll stick around NBC News, but smart money says no.

Shapiro, Capus and NBC Universal TV czar Jeff Zucker were all Ziplocked Tuesday.

Capus was promoted to NBC News senior vice president in June. He scored major points last week with his coordination of NBC's Hurricane Katrina coverage. (Shapiro was on vacation.)

Capus, 41, joined NBC in 1993. In '01, he was named executive producer of "NBC Nightly News," with Tom Brokaw, then Brian Williams.

No timetable for NBC to name a permanent successor, but the highly regarded Capus is expected to be on the network's short list.

Shapiro's resignation was no surprise. His laid-back style never really meshed with that of alpha male Zucker.

Some of the troops criticized Shapiro's leadership for waiting so long before taking charge of the increasingly tense situation at "Today," whose 10-year dominance is being threatened by ABC's "Good Morning America."

NBC's single most important cash cow, "Today" generates more than $250 million in profit a year. Like Zucker's, Capus' roots are there -- he was supervising producer in '95.

"It gives me great confidence to know that Steve will be at the helm while we navigate these complicated times," Zucker said in a staff memo. "He has touched almost every part of the division," having worked at numerous NBC broadcasts, MSNBC, and NBC News Channel.

Shapiro, 48, spearheaded the seamless anchor transition of Tom Brokaw to Brian Williams in December. He came to NBC in 1993 as executive producer of "Dateline NBC" after a 13-year tenure at ABC.

In a staff memo, Shapiro said he questioned whether he would "find the next few years as personally fulfilling as the first four" of his presidency, and that he was "missing the opportunity for the kind of creativity" he'd had in previous positions.

"Reflecting on all of this, I've concluded that it's time to move on to a new challenge." (Gail Shister, Knight Ridder Newspapers)

'REAL WORLD' SEEKING CAST

Casting producers from MTV's "The Real World" will be auditioning for new cast members in Pittsburgh on Sept. 20, 10 a.m. to 5 p.m., at Boomerang's Bar and Grill, 3909 Forbes Ave., in Oakland.

Anyone interested in auditioning must be between the ages of 18 and 24, show a photo ID and bring a non-returnable picture of themselves. (Rob Owen, Post-Gazette TV editor)

'O.C.' HITS THREE

Marissa gets kicked out of school! Summer gets a new nemesis! Sandy takes over the business he once despised!

Just another year in "The O.C." Or, in the case of all the things just mentioned, just another month.

The Fox series, which opens its third season tonight, plans to cover a lot of ground again this year, creator Josh Schwartz says. And after tying up a couple of loose ends (albeit not too tightly) in the season premiere, the show will dive into a year of changes for the Cohens and those around them.

"This year is senior year [for the teen characters] and with senior year comes all that sort of angst and anxiety, all that sort of epic teen drama -- who am I, where am I going, what's gonna happen to us," Schwartz says. "It's going to call everyone's identity into question and throw the show back on the family."

The premiere resolves the legal questions revolving around Marissa's (Mischa Barton) shooting of Ryan's (Ben McKenzie) brother Trey (Logan Marshall-Green). But Schwartz said fallout from the incident will continue to affect the characters -- starting with Marissa being kicked out of the Harbor School, thanks to a new dean of discipline ("Eyes' " Eric Mabius, who will have a recurring part).

Marissa's departure will bring a new character, Taylor Townsend (Autumn Reeser, "Complete Savages"), into the forefront at Harbor. Schwartz describes her as "this sort of steaming, young Newpsie-in-training socialite who's been toiling in Marissa's shadow all these years." With Marissa banished to (gasp) public school, Taylor takes over as Harbor's social chair -- much to the consternation of Marissa's best friend Summer (Rachel Bilson).

"Summer goes toe-to-toe with her as a sort of symbolic gesture to keep the Marissa flame alive at Harbor," Schwartz says. "It's going to bring back some of the classic, bitchy Summer -- there's really sort of an 'All About Eve' thing between Taylor and Summer."

Viewers will get substantial pieces of these plot threads in the first four episodes. And that's to say nothing of Kirsten's (Kelly Rowan) journey through rehab -- where she encounters the mysterious Charlotte Morgan (recurring guest Jeri Ryan) -- or Sandy's (Peter Gallagher) entree into the Newport Group as a sort of caretaker while his wife is away.

The big steps are by design, Schwartz says, as "The O.C.," after four episodes in September, will take most of October off while Fox televises the major league baseball playoffs and World Series. The network has asked the producers of its serialized dramas to leave viewers wanting more before they go off the air for baseball.

"For us, we've had so many cliffhangers lately, we were really looking for the final episode before baseball to be less a traditional cliffhanger and more a signal of the show being in a new place," Schwartz says. "There's a sense that the show has really moved over the course of those four episodes and set up some new dynamics." (Rick Porter, Zap2it.com)