Oct. 4, 2011 -- A woman visiting New York to celebrate her 40th birthday died trapped in the back seat of the helicopter that spun out of control and plunged into New York City's East River today.

The passengers were four members of a British family on holiday to celebrate Sonia Marra Nicholson's birthday.

The other three passengers were Nicholson's partner Helen Tamaski, her mother Harriet Nicholson and her stepfather Paul Nicholson, officials said.

Tamaski is in critical condition at Bellevue hospital. Harriet Nicholson is also at Bellevue and in stable condition. Paul Nicholson, 72, in stable condition at New York University Hospital.

Paul and Harriet Nicholson are British citizens who live in Portugal and Sonia Marra Nicholson and Helen Tamaski were living in Australia.

Three members of the family and the chopper pilot were almost immediately pulled ashore this afternoon while divers searched frantically for the final passenger. Rescue personnel immediately began performing heart compressions on one of the individuals initially pulled from the water and who appeared to be unconscious.

Sonia Marra Nicholson was recovered more than two hours after the crash at 5 p.m. and pronounced dead.

"I just hope it is the only fatality and our prayers are with those in the hospital," New York's Mayor Michael Bloomberg said.

The Bell 206 helicopter took off from a heliport at 34th Street. Joy Garnett told WABC TV that she saw the chopper lift off and almost immediately begin to spin around several times and then plunge into the river.

"He took off and spun," one official said. The pilot tried to turn it around and land, but he missed by 40 feet, officials said. The chopper landed in 50 feet of water and sank within minutes.

"Whoever was on hand, people that work here, were throwing things in to them, but the (helicopter) was upside down, its pontoons in the air," Garnett said. "We could only see two figures clutching onto the pontoons and it took about five minutes for it to sink."

Garnett said the onlookers on the dock called 911.

The pilot was identified as Paul Dudley. Dudley made a spectacular emergency landing in a Brooklyn park in 2006 when a Cessna 172 he was piloting had engine trouble. In that landing, no one was injured.

Dudley, who was rescued from the East River, is the manager at the Linden, N.J., airport. He flew his chopper to the helipad at East 34th Street to pick up his four passengers, officials said.

The chopper went down about 3:20 p.m. and within 10 minutes rescue divers were in the murky water searching for survivors, officials said.

Some of the officers who rushed to the scene were conducting a counter terror drill. When chopper went down the doffed their flack vests and dropped there automatic weapons as they raced to the river's edge.

Mayor Bloomberg praised the city's response to the crash. "A quicker response could not have happened and it wouldn't have made any difference," he said.

He said the chopper was inverted.

The mayor said flotation devices for passengers are optional in helicopters and that most don't carry them. "But if a helicopter lands upside down, they don't do any good," he said.

Ten boats from the New York police and fire departments as well as the Coast Guard and a helicopter were part of the search. Scuba teams were in the water. Some ferry service on the East River was suspended during the search.

Officials from the Federal Aviation Administration and the National Transportation Safety Board were on the way to investigate the crash.

Helicopters that fly under 1,000 feet are not in contact air traffic controllers and don't file a flight plan.

ABC News' Aaron Katersky contributed to this report