Law enforcement authorities in the city of Chelyabinsk detained a vice principal and the head of a private security company following a hammer attack at a local school earlier this week, investigators said Wednesday. Police said a 13-year-old student injured three classmates and a teacher with a hammer at School No. 68 on Monday. The student was arrested and charged with attempted murder and “negligence,” though his motives remain unclear. The school’s vice principal was also later arrested and charged with negligence, according to the Chelyabinsk branch of Russia’s Investigative Committee, wh…