A gunman killed seven people, including an unborn baby, during a shooting at a Jehovah's Witness service in Hamburg on Thursday night, German police said.
The perpetrator then killed himself after armed police stormed the building.
At a press conference on Friday, police confirmed the 35-year-old was a former member of the Jehovah's Witness community, who later professed a hatred for the group.
He has been identified as Philipp Fusz.
Police said he fired more than 100 rounds of ammunition during the attack in the hall. Hundreds more rounds were found in a search of the man’s apartment.
The German citizen legally held a licence for sport and owned a semi-automatic weapon. It is possible he had a mental illness, said police.
Hamburg police chief Ralf Martin Meyer said he was previously investigated after authorities received a tip that he might not be suitable to bear firearms, but was found not to have broken rules.
It is not yet known why he carried out the attack, but a political motive has been ruled out. Police said there was also no evidence for a terrorist link.
His victims included four men, two women and an unborn child of seven months' gestation, who was hit in the womb. The mother survived. Eight people were wounded, four of them seriously.
A quick police intervention prevented more people from being killed, said State Interior Minister Andy Grote at the press conference.
Hamburg’s top security official said officers arrived minutes after receiving the first emergency call at 9.04pm.
A special operations unit that was nearby reached the site at 9.09pm and was able to separate the gunman from the congregation, said Mr Grote.
“We can assume that they saved many people’s lives this way,” he told reporters. Mr Grote called the shooting “the worst crime that our city has experience recently”.
Shooting at Jehovah's Witness centre in Hamburg — in pictures
Police did not use their own firearms.
The head of Germany's police union in Hamburg, Horst Niens, said he was convinced that the swift arrival of a special operations unit “distracted the perpetrator and may have prevented further victims”.
Police were alerted to the shooting just after 9pm via a “catastrophe warning app”, and rushed to the scene in the Grossborstel area in Germany’s second-biggest city.
“We only know that several people died here,” said police spokesman Holger Vehren. “Several people are wounded. They were taken to hospitals.”
Gregor Miesbach, who lives within sight of the building, was alerted by the sound of shots and filmed a person entering the building through a window.
Shots could then be heard from inside. The person later emerged from the hall, was seen in the courtyard and then fired more shots inside.
Mr Miesbach told German television news agency NonstopNews that he heard at least 25 shots. After police arrived, one last shot followed about five minutes later, he said.
His video, posted online by Bild newspaper, showed the person firing numerous times into the building through a first-floor window before the lights inside the room went out.
“We heard shots,” one unidentified witness told reporters. “There were 12 continuous shots,” he said. “Then we saw how people were taken away in black bags.”
David Semonian, a US-based spokesman for the Jehovah's Witnesses, said members “worldwide grieve for the victims of this traumatic event”.
“The congregation elders in the local area are providing pastoral care for those affected by the event,” he wrote.
“We understand that the authorities are still investigating the details of this crime. We appreciate the courageous help provided by the police and emergency services.”
German Chancellor Olaf Scholz said on Friday he was left “speechless” by the shooting in his hometown of Hamburg, and his thoughts went out to the victims and their relatives.
“We fear that further victims may die from their severe wounds,” he said, thanking security forces for their work
The mayor of Hamburg expressed shock at the incident.
“I extend my deepest sympathy to the families of the victims. The forces are working at full speed to pursue the perpetrators and clarify the background,” Peter Tschentscher said on Twitter.
In a Twitter update on Friday morning, Hamburg police said they believed there was only one gunman and they were gradually pulling back security forces from the area.
“The investigation into the motive behind the crime continues,” police said.
The scene of the shooting was the Jehovah's Witnesses' Kingdom Hall, a modern and boxy three-storey building next to an car repair shop.
Mr Vehren said that after officers arrived and found people with apparent gunshot wounds on the ground floor, they heard a shot from an upper floor and found a fatally wounded person upstairs who may have been a gunman.
Police did not have to use their firearms, he said.
Mr Vehren said there was no indication that a gunman was on the run and that it appeared likely that he was either in the building or among the dead.
Through the night, forensic investigators in protective white suits could be seen walking through the building, continuing their work.
Student Laura Bauch, who lives nearby, told German news agency DPA there were about four periods of shooting.
“There were always several shots in these periods, roughly at intervals of 20 seconds to a minute,” she said.
She said she looked out her window and saw a person running from the ground floor to the second floor of the Jehovah's Witnesses hall.
On Friday morning, investigators could be seen working outside the building as a light snow fell, placing yellow cones on the ground and windowsills to mark evidence.
Police had no information on the event that was under way in the building when the shooting took place. They also had no immediate information on a possible motive. Mr Vehren said that “the background is still completely unclear”.
Hamburg Mayor Peter Tschentscher tweeted that the news was “shocking” and offered his sympathy to the victims' relatives.
Jehovah’s Witnesses are part of an international church, founded in the US in the 19th century, which is based in Warwick, New York.
It claims to have a worldwide membership of about 8.7 million, with about 170,000 in Germany. There are about 2,020 Jehovah’s Witness congregations and 170,491 ministers in the country. One in 498 Germans practice the faith, according to the denomination’s website.
Members are known for their evangelistic efforts including knocking on doors and distributing literature in public squares.
The denomination's distinctive practices include a refusal to bear arms, receive blood transfusions, salute a national flag or participate in secular government.
Germany’s gun laws are more restrictive than those in the United States, but permissive compared with some European neighbours, and shootings are not unheard of.
Last year, an 18-year-old opened fire in a packed lecture at Heidelberg University, killing one person and wounding three others before killing himself.
In January 2020, a man shot dead six people including his parents and wounded two others in south-western Germany. A month later, a gunman who posted a racist rant online killed nine people near Frankfurt.
