A bus that crashed into a bank killing a pedestrian had been parked at a stop moments before it "jolted forward" across the road, a passenger said.
Durham Police said the 52-year-old man driving the single-decker, which smashed into the front of a branch of the Halifax in Darlington, has been arrested on suspicion of causing death by dangerous driving.
An elderly woman was killed after she was trapped under the Arriva bus and two others were hurt, although their injuries were not thought to be life-threatening.
The 10.50am collision in Northgate brought the middle of the bustling market town to a standstill.
Shoppers were kept away from the scene and screens were put up to stop people from seeing the recovery operation.
Paul Frazer, 34, who works for Primark, had just finished his shift and had caught the bus heading to his Darlington home.
He said: "As soon as I sat down the bus jolted forward. It felt like a whoosh, such a fast speed."
Police said the bus went about 20 yards across the road, hitting a pillar of the bank close to its door.
Passengers were helped off the bus through the emergency exit by a Polish passer-by, said Mr Frazer, who was reassuring an elderly woman on the vehicle who looked close to tears.
He said: "I just want to say thank you to everyone who helped me off. My emotions were running high. It was a scary ordeal."
Janet Langan, a retired civil servant who lives in Branksome, on the edge of Darlington, came out of the Queen Street Shopping Centre just after the crash.
"People were being sick and people were crying and I saw a man under the wheels. Then they started to put the green screen up so I couldn't see," the 64-year-old said.
"That turning is just a death trap. It's the second time this has happened. About 18 months ago a bus went skew-whiff at the sharp turn by Boots and Halifax, but not like this.
"I use that bus - the number 2 - every day. The only reason I wasn't outside the bank is because I went to buy a tin of paint. That's what has stunned me more than anything - that I would have been there.
"I just stood with my mouth open and couldn't believe it."
Alec Deak, 31, from Darlington was walking up from the library when he saw the aftermath of the crash.
He said: "There was a gentleman in distress laid on the footpath being attended by passers-by.
"A jacket was covering what appeared to be a lady under the front wheel."
Chief Inspector Graham Milne said: "We have some very good CCTV evidence as it occurred and we are appealing for witnesses. If anyone has any information please call Durham Police on 101."
He thanked local businesses for their help.
Arriva North East said the bus was Service 2 from Branksome to Red Hall and an investigation has begun.