Buses were turned into ambulances. An emergency medical station was set up at a hotel. Rescue workers, police and ordinary people streamed into the streets to help.
Nearly simultaneous blasts on three subway trains and a red double-decker bus brought chaos to the streets of London Thursday.
Ambulances sped from the wreckage of the bus torn apart by a blast near central London's Russell Square (search). Its mangled upper deck was open to the sky and debris littered the street. The facade of a nearby building was blackened and scarred by shrapnel.
"I could see the bus with the roof ripped off and one side peeled down," said Jenny Gimpel, who was on her way to work when she saw the blasted bus. "It looked absolutely horrific."
Just a day before, London had been basking in the glory of winning the 2012 Olympic Games (search), with wild celebrations on Trafalgar Square (search). On Thursday, an eerie quiet had taken hold in some parts of the city.
"Yesterday we were quite glad that we got the Olympic bid," said Arvind Mavji, a transport worker at Euston Station, near the site of the Russell Square bus blast. "Today we are wondering if it was worth it."
Buses were pressed into service as ambulances as dozens of casualties were taken to hospitals. At the scene of several blasts, specialist emergency workers in orange biochemical suits searched for evidence of biological, chemical or nuclear agents.
At the London Hospital, a medic pumped the chest of a man who lay on a stretcher, clothes ripped and body blackened.
"There was an explosion and the flash of flames down the side of the train," said Derek Price, 55, who was on a subway train near Liverpool Street station. "It was all very quick — a loud bang happened in a matter of seconds."
Emergency workers set up a medical command post in a Hilton hotel near Edgware Road (search) subway station, where an explosion ripped through a crowded train.
Deep underground, a Swedish woman riding the subway toward the station said she heard the blast behind her train.
"Everything went black, and people threw themselves to the floor in panic," Cornelia Berg told Swedish newspaper Aftonbladet by phone.
"The car quickly filled with smoke and a lot of people used their umbrellas to try to break the windows so that we could get air. A mother with her two small children sat next to me and cried desperately."
When passengers were evacuated, there were body parts scattered around them, she said.
American Sean Barron, 20, said he helped treat the wounded at Edgware Road station.
"One gentleman told me that the floor of the train he was on was blown out, it was just gone. I believe another gentleman was ejected from the train," he said.
Gary Lewis, 32, was evacuated from a subway train at King's Cross station and described a scene of panic as medics tended to casualties brought to a ticket hall.
"People were covered in black soot and smoke. People were running everywhere and screaming. It was chaos," he said. "... The one haunting image was someone whose face was totally black and pouring with blood."
As police shut down subways and buses across the city, central London streets became all but empty of traffic. Some commuters tried to make their way to work or home on foot. Groups gathered around corner shops with televisions, watching in silence pictures of a mangled red bus.
The mood was somber and subdued, but there was little outright panic. People tried to call loved ones on cell phones, and many loaned their phones so strangers could make calls.
Many tourists in central London were caught in the blasts.
"I think these were terrorists. They were successful," said Nadia Ivanova from Bulgaria. "Their idea was to disturb society. They've reached that. Everyone is afraid now, and not only now but these last few years."
But others said they would not be deterred by the attacks,
"I think we just have to go on about our business," said Richard Bomar, a tourist from Louisville, Kentucky. "I'm just not afraid. I'm not going to let it affect me."
Taxi driver Steve Green said that despite the carnage, "people are getting on with it. It's marvelous that they're showing their backbone."
"The thing is, with us Londoners, we're used to the IRA. We don't know anything else. You don't like it, but you learn to deal with it."