Eight people died in a shooting at a Jehovah’s Witness hall in Germany, police said.
A number of people were hurt, some of them seriously.
There is still no word on a possible motive for Thursday evening’s shooting, which has stunned Hamburg, the nation’s second-biggest city.
Germany Chancellor Olaf Scholz, a former Hamburg mayor, described a “brutal act of violence”.
Overnight, police said one of the people found dead may have been the sole gunman.
Investigators worked through the night to secure evidence.
On Friday morning, forensic investigators in protective white suits could still be seen outside the building as a light snow fell.
Officers placed yellow cones on the ground and windowsills to mark evidence.
Hamburg officials said there will be a press conference on Friday afternoon to discuss the details.
David Semonian, a US-based spokesman for Jehovah’s Witnesses, said in an emailed statement early on Friday that 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.”
The scene of the shooting was a Jehovah’s Witnesses’ Kingdom Hall, a boxy three-storey building next to a car repair shop in the Gross Borstel district, a few miles from Hamburg city centre.
Police spokesman Holger Vehren said officers were alerted to the shooting at about 9.15pm and on the scene quickly.
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 the gunman, he said.
Police did not have to use their firearms, he added.
Student Laura Bauch, who lives nearby, said there were around four periods of shooting, German news agency dpa reported.
“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 upstairs from the hall’s ground floor.
Gregor Miesbach, who lives within sight of the building, was alerted by the sound of shots and filmed a figure entering the building through a window.
In the footage, shots can be heard from inside. The figure later apparently emerges from the hall, is seen in the courtyard and then fires more shots inside.
Mr Miesbach told German television news agency NonstopNews he heard at least 25 shots. After police arrived, a final shot followed about five minutes later, he said.
His video showed a person firing multiple shots into the building through an upstairs window before the lights inside the room went out.
Jehovah’s Witnesses are part of an international church, founded in the United States in the 19th century. It claims a worldwide membership of about 8.7 million, with about 170,000 in Germany.
Members are known for their evangelistic efforts which include knocking on doors and distributing literature in public spaces.
