COPENHAGEN, Denmark—A 15-year-old boy has been detained on suspicion of attempted murder after a school employee was seriously wounded in a knife attack in southern Sweden Thursday, police said. The Skanska Dagbladet newspaper said the attacker carried a long knife, wore a skeleton mask, a helmet and what looked like a bulletproof vest. Police declined to comment. Police spokeswoman Ewa-Gun Westford said the 45-year-old male victim was rushed by ambulance to a nearby hospital. The boy was arrested outside the school. A police officer fired a weapon in connection with the arrest, Westford said. The incident happened in Eslov, 22 miles northeast of Malmo, Sweden’s third-largest city. The motive for the attack was unclear, Westford said, adding it was not immediately clear whether the teenager is a student at the school. A nearby sports venue was used to gather the students and staff who were in the school building at …