Swedish police said that about 10 people, including the gunman, were killed during a shooting on Tuesday at an adult education centre.
They said a final death toll and a conclusive number of wounded had not yet been determined.
The damage at the crime scene was so extensive that investigators were unable to be more definitive, said Roberto Eid Forest, head of the local police.
The shooting happened on the outskirts of the city of Orebro, about 125 miles west of Stockholm.
Police said that the death toll could rise, and Mr Eid Forest told reporters that the suspected gunman was among those killed
Police at the scene of the shooting in Orebro (Kicki Nilsson/TT News Agency/AP)
The school, called Campus Risbergska, serves students who are over the age of 20, according to its website.
Primary and upper secondary school courses are offered, as well as Swedish classes for immigrants, vocational training and programmes for people with intellectual disabilities.
Police said that there were no suspected connections to terrorism at this point.
Police believe the perpetrator acted alone. He was not previously known to police, officials said.
Authorities were working to identify the dead. They did not immediately provide an exact number of fatalities.
Gun violence at schools is very rare in Sweden, but there have been several incidents in recent years in which people were wounded or killed with other weapons, such as knives or axes.