At least four people, including a nine-month-old baby, were killed and several more injured when a speeding car ploughed into a pedestrian area in the western German city of Trier.
Witnesses said people screamed in panic and some were thrown into the air by the car as it crashed through the shopping zone on Tuesday.
The driver, a 51-year-old German man from the Trier area, was arrested a kilometre away when the car was stopped by police.
State Interior Minister Roger Lewentz commended police on their reaction, saying that they had stopped the car and taken the suspect into custody within four minutes of receiving the first call.
Prosecutor Peter Fritzen told a news conference the suspect had drunk a significant amount of alcohol, and authorities did not currently believe there was any Islamist militant motive to the incident.
Trier Mayor Wolfram Leibe said: "It looks as if we are talking about a suspect with mental issues, but we should not pass premature judgement."
Officials shaken by 'horrible' scenes
Mr Leibe was one of the first to visit the scene and struggled with his emotions when addressing the media.
"We have an amok driver in the city. We have two dead that we are certain of and up to 15 injured, some of them with the most severe injuries," he said.
"I just walked through the city centre and it was just horrible. There is a shoe lying on the ground, and the girl it belonged to is dead."
German Chancellor Angela Merkel's spokesman Steffen Seibert called the incident "shocking".
"What happened in Trier is shocking. Thoughts are with the relatives of the victims, with the numerous injured and with everyone who is currently on duty to care for those affected," he wrote on Twitter.
Late on Tuesday officers were still scouring the area in search of evidence, backed by police dressed in flak jackets and carrying sub-machine guns, while on the streets, Christmas lights twinkled.
Germany has tightened security on pedestrian zones across the country since a truck attack on a Berlin Christmas market in 2016 that killed 12 people and injured dozens.
ABC/wires
