The student, aged 18, was taken into custody on Monday in Malmo (Sweden's third-largest municipality). Police said that the victims were two women in their 50s.
The suspect was not known to police before and didn't have any criminal records. Police also did not disclose the circumstances of the murders. It has not been determined what the motive was.
"For now, it is far too soon to comment on that," Malmo Police Chief Petra Stenkula said at a news conference.
She stated that officers arrived on the scene and located the suspect and the two victims on the third floor at downtown Malmo Latin School in 10 minutes.
Stenkula did not confirm the report of the Aftonbladet newspaper that Stenkula claimed that the male student called authorities to claim that he had called them to say that he had killed two people and had laid down his weapons. He was also on the third floor.
Stenkula stated that police made "seizures" in the case and that a forensic examination would help to understand the circumstances. Authorities don't have any information about further injuries.
Police stated that they were called Monday at 5:12 PM. Numerous ambulances and patrol cars raced to the school, and armed police were seen entering and exiting the building.
The school has approximately 1,100 students. Students gathered at the school to work on a musical, and then students locked themselves in their classrooms.
According to the Swedish news agency TT, Magdalena Andersson, Sweden's Prime Minister, said that she reacted with sadness and dismay to the murders.
All classes were suspended on Tuesday, and the school was shut down.
The murders occurred in the modern annex to the school. It was established in 1406 by the pope, who issued a letter granting permission for its construction. It was originally intended to teach local youth about Christian doctrine and Latin language.