Swedish police are investigating whether an 18-year-old man who attacked students at a high school with a sword on Friday, killing one, was involved in online communities promoting school violence, a police source said. The attacker struck at a school in the central ‌Swedish town of Fagersta, also severely injuring two teenage boys before being arrested by police. The parents of a 17-year-old girl told local newspaper Fagersta-Posten that their daughter was killed in the attack.