COPENHAGEN, Denmark (AP) — A knife-wielding masked man stabbed four people Thursday at a school in southern Sweden, killing one teacher and a student before being shot by police, authorities said. One student said he thought the attacker was in a Halloween costume.

A police official in Sweden says a man who killed two people and wounded two others in a deadly knife attack at a school has died.

Police spokesman Thord Haraldsson said Thursday the attacker died after being shot by police who responded to the school in Trollhattan, near Goteborg, Sweden's second-largest city.

He told a news conference that the masked attacker knocked on the doors to two classrooms and stabbed the people who opened the doors.

Students fled from the Kronan school in Trollhattan as the attack took place in a nearby cafe just after 10 a.m., police said. The school has 400 students, ranging from pre-school to high school.

Police arrived to find one male teacher already dead and two male students and another male teacher seriously wounded, police spokesman Thomas Fuxborg told The Associated Press. One of the students died later at the hospital.

Police fired two shots, one of which hit the attacker, a 21-year-old man from Trollhattan, Fuxborg said. The attacker's motive was not known, he added.