The Glasgow bin lorry driver who lost control of his truck said the moment he blacked out was "like a light switch".
Six people were killed when the lorry driven by Harry Clarke, 58, veered onto the pavement on December 22 last year.
Mr Clarke gave an account of the day of the accident during evidence at an inquiry into the tragedy.
He said: "Everything was okay, I saw the Christmas lights in the distance, and the next minute ... it was like a light switch."
The driver said the next thing he remembered was "being attached to the hotel" - the Millennium Hotel in George Square where the truck came to rest.
He said: "I think I remember (bin man) Matt shouting 'Harry, wake up'. It was as if he was a mile in the distance.
"I came to and I didn't know what had happened to me, I couldn't understand it. Matt was there, I said 'Matt, what happened?' and he couldn't talk to me.
"Wee Henry (another bin man), he was in tears apparently, which you can understand."
During earlier evidence, Mr Clarke was asked questions about his medical history which he refused to answer.
Sheriff John Beckett told him he did not have to give any responses that might incriminate him as he could face prosecution by the families of the crash victims.
The council worker began giving a full account of the day of the accident after being pressed by Solicitor General Lesley Thomson QC, the senior law officer leading the inquiry, who told him: "I am going to ask you questions about December 22.
"There are a lot of people over there (pointing to victim's family members) who want to hear the answers."
She told Mr Clarke "to think about your choices" after previously suggesting he was putting himself before the inquiry.
The driver said he was "feeling brand new" the day of the tragedy and his crew Matthew Telford and Henry Toal were their normal selves as they chatted about Christmas during the afternoon waste collection trip in the city centre.
He told the inquiry he ate a chicken and mushroom Pot Noodle for lunch that day - and has not had one since - plus a packet of crisps and a biscuit.
Mr Clarke was asked about three unopened beer bottles found in the truck cab after the accident and explained that it was common for the crew to receive gifts from shop owners around Christmas time.
After the crash he said he remembered being helped out from behind the wheel and down from the truck by a fireman and an off-duty nurse.
He said: "I looked round about ... I didn't know what had happened. My speech was slurred. I knew who people were but I was very confused."
Mr Clarke was asked if he knew about the people who had been injured and he said his view of the scene was blocked by fire engines and police cars.
He began taking deep breaths and appeared to become emotional, telling the inquiry: "I couldn't really see anything, but ... what can I say?"
The inquiry has heard evidence that Mr Clarke has a history of dizzy spells and fainting which he failed to disclose to the DVLA and on job application forms.
Mr Clarke began his first day in the witness box at the FAI by refusing to answer a number of the questions he faced.
In answer to the majority of questions put to him in the morning session, Mr Clarke responded: ''I don't want to answer that'' or ''No comment''.
Mr Clarke was asked by the Solicitor General: "Do you understand that by choosing not to answer you are putting yourself first?"
He replied: "I wouldn't agree with that."
During subsequent evidence, the witness was asked to look at his medical records dating back to June 1976 which listed periods of dizziness and ill-health.
Following an interjection by his lawyer, Mr Clarke said: ''I don't wish to answer any more questions.''
The witness was also asked about his time as a driver with First Bus, where the inquiry has heard he worked before joining Glasgow City Council in 2011.
He was questioned about an incident on April 7 2010 when he is said to have blacked out at the wheel of a bus in the city.
He was asked: ''Do you recollect an incident where paramedics came to see you after a medical incident on a bus?'' He said he did not want to answer.
Mr Clarke appeared before the inquiry after a motion from his lawyer, Ronnie Clancy QC, to have the hearing halted was rejected.
The sheriff said it was in the public interest that the inquiry should proceed.
Erin McQuade, 18, and her grandparents Jack Sweeney, 68, and Lorraine Sweeney, 69, from Dumbarton, West Dunbartonshire, Stephenie Tait, 29, and Jacqueline Morton, 51, both from Glasgow, and Gillian Ewing, 52, from Edinburgh, were killed as the lorry travelled out of control towards George Square before crashing in to the side of the Millennium Hotel.
The Crown Office has already decided that Mr Clarke should not be prosecuted over the fatal crash.
But relatives of Ms Morton have indicated that they would seek to bring charges against Mr Clarke.
The inquiry was adjourned until tomorrow when Mr Clarke will continue giving evidence at 9.30am.