The young man was arrested within the grounds of the school, the newspaper reported.
“It feels completely unreal that our school is affected. I can not remember a single incident here before,” an unnamed student told Aftonbladet.
At the time they were called out, police classed the incident as a case of “ongoing lethal violence” and a “serious crime incident”.
By 6.30pm, they said that they had the situation “under control”, although the local unit of the Swedish Police’s National Task Force was at that time still searching the school buildings.
Hours after the incident, many of the pupils who had been at the school were still being kept inside by police, an ambulance was still in place, and the road outside the school had been blocked and cordoned off.
Most of the school’s pupils had already returned home by the time the reported attack took place, and only an estimated 50 pupils were still there, some to play sports, and others, reportedly, to rehearse for a musical.
“This is an extremely serious event, but our judgement is that there is no danger now. Everything points to the fact that there was only one perpetrator,” Evelina Olsson with the Malmö police told The Telegraph shortly after the incident. She said a gun had not been used.
“We want to collect as much information as possible, to interview all the pupils, and we also have forensic technicians on site,” she added.
Johan Kullenbok, a teacher at the school, told the Telegraph that police wielding guns had come into the school just as he was packing up for the day.
“I was told to stay in my office, which I did…I was just there for two hours with another teacher, while the police searched the building,” he said.
Fredrik Hemmensjö, the school’s headmaster, told Aftonbladet newspaper that the situation was “absolutely terrible”.
“All I know is that the school is facing deadly violence. I wish I knew more,” he said from the city of Gothenburg, where he was away on a visit.