Other videos showed broken windows with debris outside and emergency service vehicles parked outside the school, with people running towards the building.
"The terrorist has been arrested, (he is) 19 years old. He's 19. He's a registered firearm owner". Minnikhanov said it wasn't clear yet whether the gunman had accomplices or acted alone.
The victims at Kazan's School No. 175 some 820 kilometers east of Moscow include one teacher, one female school employee and seven eighth-grade students - four boys and three girls, the republic of Tatarstan's head Rustam Minnikhanov told state media.
Investigative authorities say a gunman opened fire in the school and triggered an explosion.
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Chauvin was also charged in a second indictment, stemming from the arrest and neck restraint of a 14-year-old boy in 2017. Chauvin was convicted of second-degree unintentional murder, third-degree murder and second-degree manslaughter.
A total of 21 people have been hospitalized, including 18 children and three adults.
While school shootings are relatively rare in Russian Federation, there have been several violent attacks on schools in recent years, mostly carried out by students. But most of the proposed legislative changes were turned down by the parliament or the government, the Kommersant newspaper reported.
Local media initially reported that there were two suspects but authorities later said the incident was carried out by a lone attacker.
President Vladmir Putin has ordered an "urgent" tightening of gun control restrictions in the wake of the shooting, which took place on the first day back to school after a 10-day holiday, Kremlin spokesman Dmitry Peskov said. Russian officials promised to pay families 1 million rubles (roughly $13,500) each and give 200,000 to 400,000 rubles ($2,700-$5,400) to the wounded.