Candles were lit and flowers laid in front of the cordoned off Campus Risbergska school for young adults in Orebro as residents flocked to pay their respects.
"We are very shocked," King Carl XVI Gustaf told reporters, after he and Queen Silvia laid flowers near the school, highlighting the country's struggle to understand events.
"All of Sweden is mourning today."
Police have not given details on the gunman or his motive. But they confirmed that 11 people, "including the killer", died in Tuesday's shooting spree in the town west of Stockholm.
Prime Minister Ulf Kristersson, who also visited the site Wednesday, has described the massacre as "the worst mass shooting in Swedish history".
"Tuesday, February 4 will forever mark a dark day in Swedish history," he said in a statement.
Asked about reports that the gunman turned his gun on himself, Orebro police chief Roberto Eid Forest told reporters that "there is a lot to indicate that".
Forest told a press conference the suspect was dead when police reached him.
Police were working to establish the reason for the killing spree, and had not seen an indication of an "ideological motive", he said. The suspect was not previously known to police.
- Six in hospital -
"I can't say more about the suspected perpetrator, other than that he was obviously motivated and had access to firearms," Lars Wiren, regional police chief, told AFP.
"When the first police officers entered the building shots were fired, likely at the police, but no one of our staff is injured," Wiren added.
Police said not all the victims had been fully identified and have not disclosed any information about them.
Health authorities said six people were being treated at Orebro's university hospital.
Three women and two men had undergone surgery for gunshot wounds and were in a "stable but serious" condition.
A woman was treated for minor injuries, Orebro County authorities said in a statement, adding that all the wounded were over the age of 18.
Kristersson has invited all of Sweden's political party leaders to a meeting on Thursday that would begin with a minute of silence.
"We are a country in mourning, and we must all come together," he said.
- 'Numb, speechless' -
The TV4 television channel reported that police raided the suspected gunman's home in Orebro on Tuesday. It said the man was around 35 years old, licensed to carry a weapon and had no criminal record. Reports have not identified him however.
The man lived reclusively, was unemployed, and had distanced himself from his family and friends, Aftonbladet newspaper reported, citing family members.
The attack was carried out about midday on Tuesday.
"I saw some bodies lying on the ground. I don't know if they were dead or injured," 16-year-old Linn, who goes to school near the site of the massacre, told AFP.
"There was blood everywhere, people were panicking and crying ... it was chaos," she added.
"I became numb, speechless. I didn't really know where to go," Liv Demir, 36, whose son attends a school near Campus Risbergska, told AFP.
Her son has gym classes at Campus Risbergska. "My thoughts were spiraling because I packed his sports bag in the morning," Demir said.
- 'Dark hour' -
Sweden's Royal Court announced that flags would be "flown at half-mast at all royal palaces". The government announced a similar measure for its offices and parliament.
European Commission president Ursula von der Leyen called the shooting "truly horrifying".
"Such violence and terror have no place in our societies -- least of all in schools. In this dark hour, we stand with the people of Sweden," she said in a post on X.
School attacks are rare in Sweden, but the country has suffered shootings and bombings linked to gang violence that kill dozens of people each year.
In March 2022, an 18-year-old student stabbed two teachers to death at a secondary school in Malmo. Two months earlier, a 16-year-old wounded another student and a teacher with a knife at a school in the small town of Kristianstad.
In October 2015, three people were killed in a racially motivated attack at a school in the western town of Trollhattan by a sword-wielding assailant who was killed by police.
© Agence France-Presse
