A time of celebration quickly turned into one of sorrow.
Beneath the bright Berlin lights of the popular Christmas markets outside the Kaiser Wilhelm Memorial Church in the heart of former West Berlin, holiday shoppers were mowed down.
Eyewitnesses have described the shocking scenes.
"A truck drove in there and simply drove over people, and then I was over there. I saw how it drove in there, and then he ran away."
British tourist Mike Fox says the truck ploughed through as he and his girlfriend were leaving the markets.
"It went just past me, past my girlfriend. I think it missed me by three metres, missed her by five. It came in through the entrance, hit the sides of the barriers and then carried on past us."
Bodies were scattered across the once-bustling marketplace in a scene that had rescue crews in a state of shock.
Berlin Fire Service spokesman Sven Gerling explains.
"We had a first phase here in which many people were calling for help, many people were injured, some of them so severely injured that they could not talk."
The driver, reportedly a Pakistani migrant, fled on foot when his truck finally came to a halt.
But Berlin police spokesman Thomas Neuendorf says he didn't get far, apprehended just a few blocks away.
"The police took up the chase, followed him, and arrested one suspect. He is at a police station now and is been questioned."
German police now believe the carnage was intentional, presumably a terrorist attack, they said.
Earlier, Thomas Neuendorf told the media they were erring on the side of caution.
"The investigation is ongoing, we have no indications in one direction or another. All of this is subject of the investigation."
Those comments were echoed by Berlin Interior Minister, Andreas Geisel.
"I caution everyone not to jump to conclusions and change our way of life. It is too early for that. And that is why I don't want to speculate any further or announce anything here."
But witnesses such as Emma Rushton have recalled the lorry jumping the curb at speed, accelerating to over 60 kilometres per hour (40 mph) with the headlights switched off.
She believes that's evidence of intent.
"There's a main road to the side of it, but there's no way it could come off that as an accident. It went through the middle of the market."
The truck was reportedly stolen outside a worksite earlier in the day.
Its original driver, a Polish citizen, was found dead in the passenger seat.
The truck's owner, Ariel Zurawski, says that man was his cousin.
There had been warnings that Christmas markets were vulnerable targets.
Questions are now being raised by witnesses as to why this location wasn't more secure.
"How can I feel safe? And how can you trust people, security people any longer? I can't, not any more."
The attack puts further pressure on German Chancellor Angela Merkel, who has already suffered a drop in popularity because of her decision to accept hundreds of thousands of refugees.
The tragedy has been compared to the deaths of 86 people in Nice, France; when a large truck mowed down crowds watching Bastille Day fireworks in July.
