Eleven people were killed in a shooting at an adult education centre on Tuesday, Swedish police said, marking the country’s deadliest gun attack in what the prime minister called a “painful day.”

Police said the gunman was believed to be among those killed and a search for other possible victims was continuing at the school, located in the city of Orebro. The gunman’s motive was not immediately known.

Later in the evening, the police website said: “At this time, there are 11 deaths due to the incident. The number of injured is still unclear. We currently have no information on the condition of those injured.”

Forest told the press conference police believed the gunman had acted alone and that terrorism was not currently suspected as a motive, though he cautioned that much remained unknown. He said the suspected gunman had not previously been known to police.

The shooting took place in Orebro, some 200 km (125 miles) west of Stockholm, at the Risbergska school for adults who did not complete their formal education or failed to get the grades to continue to higher education. It is located on a campus that also houses schools for children.