Eyewitness Paul Robinson witnessed the incident yesterday in Central London when a helicopter collided with a high rise crane.
He said he was 'shook up' and his first reaction was to run away from the scene.
Two crane drivers told the Daily Mail that they were lucky to be alive after over sleeping, and missing the crash.
Tributes have been paid to the pilot of the helicopter, Captain Peter Barnes, a hugely experienced airman with an incredible career in the skies, from air ambulance pilot to flying for big budget films.
Sejal Karia reports
Patrick Banks, a close friend of Captain Pete Barnes, told ITV London that friends will "rally round" the family of the late pilot.
"He was such a genuinely nice guy," said Mr Banks.
"He'd been all over the world flying all sorts of aircraft, in particular helicopters."
The AA president Edmund King has paid tribute to the Midlands Air Ambulance killed this morning calling him a 'dedicated pilot'.
Mr King added that he was 'instrumental in helping road safety' as he flew air ambulances at the time supported by the AA.
The Automobile Association president also commended one of his rescues in 2004 when a motorist was saved from the top of his car in a flooded ford in County Durham.
Mr Barnes was also once the pilot of Newcastle Traffic and Travel helicopter as the voice of Metro FM.
A racing driver has paid tribute on Twitter to the Midlands Air Ambulance pilot killed this morning when the helicopter he was flying crashed into a London crane.
Jolyon Palmer who competes in the Formula One feeder GP2 series said Mr Barnes saved his life in 2007.
The racing driver tweeted: Pete Barnes helped save my life in 2007 after I had a serious quad bike accident. Extremely sad news today."
Loughborough MP Nicky Morgan says she "heard an almighty bang" and "saw clouds of thick black smoke" as the helicopter crashed into a crane in South London this morning.
The MP was walking towards Vauxhall tube station, when the accident happened.
"Ms Morgan says she "saw clouds and clouds of thick black smoke billowing from the ground" and that initial thoughts were that a bomb had exploded."
Midlands Air Ambulance pilot Pete Barnes who was killed this morning when the helicopter he was flying struck a London crane had a 'flying career' spanning 18 years.
Flying Air Ambulances for Derbyshire, Leicestershire and Rutland he had amassed 9,000 hours of flying time which included 3,500 hours on the type of helicopter he was flying today.
His career included work on high-profile film projects such as TV programmes and films including the James Bond film Die Another Day.
On Pete Barnes' Linked In page, a social media site, it states that he attended the University of Derby and went to school in Rutland.
The pilot of the helicopter which crashed in central London had thousands of hours of flying experience including for films such as Die Another Day and Saving Private Ryan.
Pete Barnes, who died when the helicopter he was flying hit a crane on a high building and crashed onto a street in Vauxhall, had amassed around 9,000 hours of flying time, including 3,500 hours on the type of craft he was piloting today.
The Air Ambulance have paid tribute to the Midlands pilot killed this morning in London when the helicopter he was flying struck a crane.
The Air Ambulance Chief Executive Andy Williamson said:
“We are deeply saddened to hear the news that Pete Barnes was killed in the helicopter accident in London this morning .
“Pete had worked with us for many years and will be greatly missed. Our thoughts are with his family and with all the families affected by this tragedy.”