Police were alerted to the school in the town of Kristianstad shortly after 9am on Monday, after receiving a report that at least one person had received injuries from a knife.
“He entered our classroom with a speaker playing music and a black ‘corona mask’. At first we thought it was a prank,” an unnamed student told newspaper Dagens Nyheter.
The assailant then turned towards the teacher and “started kicking”, the student said, adding that the class then started running out of the building.
Just seven minutes after the initial call, the police were able to arrest the suspect in a “relatively undramatic” way, local police chief Anders Olofsson told reporters.
A teacher, aged 55, and another student, aged 16, were injured in the attack.
The teacher’s injuries were “mild”, while the student’s injuries were described as “severe,” according to a statement published by regional health authority Region Skåne.
Police said the arrested suspect was born in 2005 and was being held suspected of attempted murder.
Later in the afternoon, broadcaster TV4 reported that the case had a connection to another similar attack in the town of Eslöv, about 50 kilometres southwest of Kristianstad, in August when a student with Nazi sympathies attacked a 45-year-old school employee.
According to TV4, the Eslöv attacker and the suspect in Kristianstad “knew each other, had been in touch with each other over the internet and shared an interest in school attacks”.