Multiple people were killed and others seriously injured in a shooting at a Jehovah’s Witness hall Thursday night in Hamburg, according to police.

Police said they received reports of the shooting at about 9 p.m. local time in the northern harbor city, where Chancellor Olaf Scholz previously served as mayor and his predecessor Angela Merkel was born. Local media reported that either six or seven people were killed during an event for Jehovah’s Witnesses. A shot was fired after officers arrived on the scene and a fatally injured person was found on an upper floor of the building who may have been the shooter, though this is still not certain, according to reports.

Police said on Twitter that the motivation for the attack is still under investigation and urged people not to spread rumors online.

Authorities initially sent a warning advising locals to avoid the area and remain indoors temporarily.

Hamburg Mayor Peter Tschentscher called the news “shocking.”

“My deepest sympathies are with the relatives of the victims,” Tschentscher tweeted. “Emergency services are working intensively to trace the perpetrator(s) and clarify the background.”