The sources said that the first signal from a panic button at the school came in at 9.25am (local time), after the shooting had started five minutes earlier. "He's a 19-year-old who was officially registered as a gun owner", Minnikhanov said. Minnikhanov said it wasn't clear yet whether the gunman had accomplices or acted alone.
A gunman launched an attack on a school in the Russian city of Kazan that left at least nine people dead Tuesday - including seven youngsters - and sent students running out of the building as smoke poured from one of the windows.
Images showed armed officers from the Federal Security Services (FSB) storming the school building, while the area was cordoned off with police tape.
A total of 21 people have been hospitalized, including 18 children and three adults.
Russian President Vladimir Putin has ordered the urgent tightening of civilian weapons control following the deadly school shooting, Kremlin spokesperson Dmitry Peskov said on Tuesday.
Authorities announced a day of mourning on Wednesday and canceled all classes in Kazan schools.
While school shootings in Russian Federation are relatively rare, there have been several in recent years - mostly carried out by students. Among them were 12 children, four of whom are in intensive care.
In 2018, a teenager killed 20 people at his vocational school before killing himself in Kerch, a city in the Russian-annexed peninsula of Crimea.
Local media initially reported that there were two suspects but authorities later said the incident was carried out by a lone attacker.