After several people were killed Tuesday at a high school in the central Russian city of Kazan, here is a list of some of the worst school shootings worldwide in the past two decades.
Two former pupils shoot dead eight people, most of them students and staff, at a high school near Brazil's biggest city on March 13, 2019 before turning their weapons on themselves.
An 18-year-old gunman kills 20 people including nine children and injures dozens before killing himself at a technical college where he was a student in Crimea on October 17, 2018.
Ten people, including eight students, are killed on May 18, 2018 when a 17-year-old student armed with a shotgun and a revolver opens fire just as classes are starting at his school in Santa Fe.
A 19-year-old former student at Marjory Stoneman Douglas High School who was expelled for disciplinary reasons returns there on February 14, 2018 and opens fire killing 14 students and three adult staff.
In a massacre that shocked the US, a 20-year-old gunman kills his mother then storms the Sandy Hook elementary school in Connecticut where he kills 20 six- and seven-year-old children and six staff members on December 14, 2012.
Rio de Janeiro
A 24-year-old former student opens fire in a school in Rio de Janeiro, Brazil, killing 12 people and wounding several others on April 7, 2011 before taking his own life.
A gunman kills 11 people including himself at a training school at Kauhajoki in the west of the country on September 23, 2008.
A South Korean student kills 32 people on his campus at Virginia Tech in Blacksburg, Virginia on April 16, 2007 before committing suicide.
Chechen rebels storm a school in Beslan, North Ossetia on September 1, 2004, taking almost 1,200 people hostage. The 52-hour siege ends with an assault by Russian special forces that leaves 331 hostages dead, including 186 children, and around 400 wounded. Thirty-one rebels die.
A 19-year-old former student, apparently in revenge for having been expelled, guns down 16 people including 12 teachers and two students at a school in Erfurt on April 26, 2002. He then kills himself.
In one of the most infamous mass shootings in US history, two youths aged 17 and 18 armed with guns and home-made bombs massacre 12 students and a teacher at Columbine high school in Colorado on April 20, 1999, before they both commit suicide.