Casualties from the London bus bomb were treated by doctors at the British Medical Association headquarters.
Dr Laurence Buckman treating a man wounded in the bus blast
The blast on board the double-decker bus went off just outside BMA House in Tavistock Square, central London.
The building became a mini-hospital as doctors treated nearly 20 people alongside ambulance crews, BMA member Dr Laurence Buckman said.
But despite the efforts of the doctors, many using skills not practised in years, two people still died.
Dr Buckman, a London GP and member of the BMA's GP committee, said: "The most extreme thing I first noticed as I walked in was that there was someone in bits in the road.
And he added: "When I arrived the most amazing things was the amount of blood everywhere, plastered across the front of the BMA.
"Then I looked on the ground and you could see where the blood was coming from.
"There was also a lot of smashed glass and metal everywhere."
The BMA House was splattered with blood
He said BMA doctors were taking patients inside the courtyard of BMA House and administering drips and stemming bleeding and treating patients for shock after the explosion.
He said around nine people were seriously injured, two of which died. Another nine with minor injuries were also treated.
He said he saw the bus driver, and he appeared to be uninjured.
But he said ambulance crews told him 10 people had died in the bus blast.
Dr Peter Holden, chairman of the BMA's professional fees committee, said the fortuitous proximity of skilled medical practitioners undoubtedly helped saved lives.
Dr Holden was in BMA House when the bus exploded and waited a short time in case there was a secondary device before going out to attend to patients.
He said that around 14 doctors and a nurse worked alongside ambulance staff to treat casualties, including several who were very seriously injured.
"Our doctors were on the scene first.
"Many of these doctors had not used these skills for upwards of 20 years but it is amazing what the human body and mind can do when the skills are remembered."
He said the treatment that was given to casualties was "like the sort of thing you see on ER".
Dr Holden said once the ambulance staff arrived with equipment, the doctors were able to do even more to help the patients.
"But people were doing the things that mattered to help save lives even before the ambulance service arrived," he said.
Dr Mary Church was also among doctors who went to the aid of the wounded.
"One of my colleagues is highly trained in emergency treatment and he had taken over and organised us into proper groups," she told the BBC.
"We prioritised the more serious down to the walking wounded.
"There was a variety of injuries, there was limb injuries, and head injuries and neck injuries and there was a lot of lacerations."
BMA House has now been evacuated and the front of the building cordoned off as forensic teams move in.