A masked man stabbed to death a teacher and seriously injured at least four pupils at a school in south-west Sweden, before he was shot by police.

A masked man stabbed to death a teacher and seriously injured at least four pupils at a school in south-west Sweden, before he was shot by police.

The attacker is being treated in hospital for gunshot wounds, according to reports. There were conflicting reports on whether he was carrying a sword or a knife.

The man, said to be in his 20s, entered the school in Trolhättan, an industrial city near Gothenburg, at around 10am on Thursday. Students locked themselves in classrooms and cupboards to escape the attacker.

Police spokesman Thomas Fuxborg told the Associated Press the attacker carried more than one weapon, including “at least one knife-like object”. Fuxborg said police fired two shots, one of which hit the attacker.

           “When we first saw him we thought it was a joke. He had a mask and black clothes and a long sword. There were students who wanted to go with him and hold the sword,” a student told Swedish media.

Some witnesses said the attacker was wearing a Star Wars mask. Others took it to be a Halloween prank.

A statement from the hospital said: “We have four seriously injured patients. All are in surgery right now. One is a teacher and two are students. One is 11 and one 15 years old. They have knife wounds. One of the injured is the suspected culprit. He is being operated on for gunshot wounds. A teacher died at the scene.”