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.