Shots were fired inside a building used by Jehovah’s Witnesses in the northern German city of Hamburg on Thursday night, killing or injuring an unspecified number of people, police said.

The shooting took place in the Gross Borstel district, a few kilometers north of the center of Germany’s second largest city.

“We only know that several people died here; several people are injured, they were taken to hospital, says police spokesman Holger Vehren.

He said he had no information on the severity of the injuries sustained by the injured.

Local media footage showed a large police presence outside the Jehovah’s Witnesses Kingdom Hall, a modern three-story building.

Vehren said police were alerted to the shooting around 9:15 p.m. and were quickly on the scene. He said after officers arrived, they heard a gunshot from upstairs and found a person upstairs who may have been the shooter. He said the police did not need to use their firearms.

Vehren said there were no immediate signs that a shooter was on the run and that it appeared likely the shooter or shooters were either in the building or among the dead.

Police had no information about the incident that was going on in the building when the shooting took place.

They also had no immediate information about a possible motive. Vehren said that “the background is still completely unclear.”

Hamburg mayor Peter Tschentscher tweeted that the news was “shocking” and offered his sympathies to the victims’ relatives.