He had left Yemen, the site of the Cole attack, because officials feared he could have been a terrorism target himself.
O'Neill had not been heard from since Tuesday morning.
Waiting for Word
Jacqueline Gavagan, seven months pregnant and home with 3-year-old twins, is hoping her husband may have been among those already rescued.
Two friends who worked near her husband, Donald Gavagan, at Cantor Fitzgerald, a legal information firm on the 104th floor of the World Trade Center, have been rescued, Gavagan said. She hopes that bodes well for her own loved one.
"I'm hoping my husband didn't have a wallet on him and he's with them," she said from her home in Brooklyn.
Jackie Rogan has been desperately seeking information about a friend, Billy Wik, who worked for the AON corporation near the top of Tower Two.
"We called every hospital in the tri-state area," she said. But she has found no news about him. She says that she and Rogan's wife are now waiting by their phones, because there is no central assembly areas for worried relatives.
"There is no place to go," she said.
Rogan said Wik had called his wife moments after Tower One was hit.
"He said, I'm gonna get out, but I have to get my people out,'" Rogan said.
No one has heard from him since.
The 44-year-old insurance executive has three children, ages 16, 12, and 8.
A Rescue Worker Phones for Help
Joyce Karnes said she got a call late last night from her brother, a former policeman and Marine who had driven from Pennsylvania to the disaster site in New York City to help in the search.
He found two police officers trapped in the rubble, but couldn't find anyone around him to help get them out.
The officers apparently were in the lobby of one of the towers when it collapsed on top of them.
"They were evidently under a lot of rubble in an air pocket," Karnes said.
Karnes called 911 with details about her brother's location, and they extricated the officers.
"He's doing good. I last heard from him at 9:30," Karnes said. "He was going back in."
Computer Executives, Ice Hockey Officials on Hijacked Planes
David Angell, of Pasadena, Calif., was one of the creators of the television show, Frasier. He and his wife Lynn were also on American Airlines Flight 11 from Boston, which crashed into the first World Trade Center tower Tuesday morning.
There were at least two high-placed computer executives among the victims. Daniel Lewin was co-founder and chief technical officer of an Internet company based in Cambridge, Mass.
The plane also carried Ed Glazer of California, an executive at fiber optics company MRV Communications.
"I made him promise me he would call me as soon as he got to L.A. because I never liked him flying, and then he told me he had to go because they had to take off for the runway," his wife, Candy Glazer, said this morning.
There were two prominent members of the professional ice hockey community, Garnet "Ace" Bailey, director of pro scouting for the Los Angeles Kings hockey team once a star player himself, was on United 175 headed from Boston to Los Angeles. Bailey was 53 and is survived by his wife and son. On the same flight was Mark Bavitz, a scout for the L.A. Kings.
And there are many more. The airlines have begun releasing partial passenger manifests today, and the grueling work of rescuing victims at the World Trade Center and the Pentagon has only begun.
St. Vincent's Hospital and Bellevue Hospital, the two main facilities handling casualties from the New York attacks, report a couple hundred injured and four fatalities, but experts say that is hardly good news.
The low numbers show how little progress has been made in searching through the rubble of lower Manhattan for the hundreds, maybe thousands trapped underneath.
Andy Serwer, ABCNEWS.com's Wall Street columnist, said he learned Tuesday that a friend had been killed in the WTC attacks.
"Sending e-mails and making phone calls was like playing Russian roulette," he said.