The helicopter crash was witnessed by many residents who live nearby and commuters who were on their way to work in the rush hour.
Sarah-Beth Casey lives in an apartment near the incident.
She told Sky News: "You're always worried about things like 9/11 and things like that. I have three small children with me in the flat. It's one of your fears that something like this can happen.
"When I heard the explosion - it was like a little earthquake."
She went on: "It was like a gas explosion. I looked up to see debris falling off the tower.
She added: "I can't see any people on the ground, it seems to be a lucky escape. The police and ambulance response was incredible."
Eyewitness Lee McPherson, 24, was near Vauxhall at the time.
He told Yahoo! News: "There was fire everywhere and buildings nearby were in flames.
"We saw lots of wreckage on the floor - you couldn't tell it was a helicopter as it was just a lot of broken metal.
"There was a VW car on fire nearby as well but the people managed to get out unhurt."
A construction worker, who did not wish to be named, saw the drama unfold. He told Yahoo! News: "I heard a loud bang, looked up and saw the helicopter coming down.
"By the time we got to the scene it was a pile of metal on fire - I could just about work out the engine, but I couldn't work out anything else.
"We tried to get a bit closer but there were five or six more small explosions."
Eyewitness Steve Carslake told BBC Radio 5 Live that he saw a car explode with someone apparently trapped inside.
Mr Carslake said he had got out of a van in Mill Street and saw the aircraft hit the crane.
He said: "We heard a mighty bang, looked up and saw the helicopter just catch the edge of the crane.
"It didn't hit the tower block itself, it hit the crane and then just came down in a fireball.
"We ran round the corner.
"We heard someone was actually trapped in the car. We went to run towards the car and there was just a large explosion again.
"It was quite devastating to watch, I'm afraid.
"It was very, very sad to watch."
[Related article: Two dead after helicopter crashes into crane in central London]
Mark Louis Sidney, who was heading for Vauxhall station, said: "I heard a loud bang, I looked up and saw bits of propeller and parts of the aircraft falling off it and then plummeting down. Then a plume of smoke went up.
"I called the emergency services. It happened in a matter of a seconds before it was on the ground. I thought 'Wait a minute, has this thing been shot out of the sky or what?'.
"I could see the top of the crane was shaking on the top of the building. It was very foggy so the helicopter probably couldn't see it."
Mr Sidney said the emergency response was "very professional" and there was "no delay".