Students from the Easy School, a language school in the Russian city of Irkutsk, gathered outside a mall on Sunday to carry out a flash mob for St Patrick's Day when they were suddenly attacked.
"Some young people came up to them and expressed displeasure at what was happening," a police spokesperson told Interfax, a Russian news agency. "There was a conflict, which turned into a fight on the square in front of the mall."
The attackers had mistaken the gathering for an LGBT rally and violently rushed the crowd, an unidentified security source told the news agency. The students who had gathered for the flashmob "were wearing historic costumes, particularly kilts, and their opponents mistook them for representatives of non-traditional sexual orientation," the source said.
The school posted the video of the incident to VKontakte, a Russian version of Facebook. It confirmed that both students and teachers were injured in the brawl.
"Yes our students and teachers were among the injured but it could have been any young people who weren't to the taste of these grey masses," Easy School said in a statement, according to Pink News. The police spokesman told Interfax that one teacher had sought medical help but did not need to be hospitalized.
Much of Russian society holds anti-LGBT views, a sentiment that has grown after the country enacted a series of anti-LGBT measures, including a law banning so-called "gay propaganda." Russia's ill treatment of the LGBT community came under heavy international scrutiny in the lead-up to the 2014 Winter Olympics in Sochi. Now that the Games are over, activists worry that cases of attack will go increasingly unnoticed.