One of the two suspects, a 31-year-old man, was seriously injured when jumping from a window on the third floor.
Anton Strand, the suspected killer's lawyer, would not comment on his client's condition, or his response to the allegations.
Martin Cullberg, the lawyer of the 28-year-old brother, maintains that his client denies the crime.
Prosecutor Ewa Tvengström, who is leading the murder investigation, would not give information about the possible motive or the details surrounding Saturday's incident.
“I don't have much to say. It is an ongoing investigation and investigative measures are being taken now,” she told the TT news agency.
The younger brother will be questioned over the course of Monday afternoon. According to Tvengström it is not yet clear whether his 31-year-old brother is in any state to be interrogated.
“That's one of the things I am trying to find out right now,” she said.
Students and staff at the girl's school have placed candles and flowers by the flagpole on the school yard in her honour.
“They're all reacting in different ways. Many feel sorrow, shock, and that it can't really have happened,” said the school principal to TT.
The school day began with everyone gathering in the canteen to talk about what has happened and how the students can receive help in dealing with the grief.
Many were already aware of the death of their friend.
In one of the classrooms the students have been given the opportunity to write messages in a book, to light candles and to leave flowers.
“We have focussed on giving support to our students and we will be monitoring them closely to see that they are able to deal with the grief,” said the principal to TT.