MOSCOW—A student opened fire Monday at a university in Russia, leaving six people dead and 28 hurt, before being shot by police and detained, officials said. Beyond saying that he was a student, authorities offered no further information on his identity or possible motive. During the attack, students and staff at Perm State University locked themselves in rooms, and video posted on Russian news sites showed some students jumping out of second-story windows. In some footage, a black-clad, helmeted figure could be seen striding on a campus sidewalk cradling a long-barreled weapon. Russia’s Investigative Committee, the country’s top body for criminal probes, said the gunman fired a smoothbore hunting weapon. That could indicate he used a shotgun. The Investigative Committee said six people were killed, revising down its earlier figure of eight dead. No explanation was given for the change. A traffic police unit was the first to reach the …