Whether this was an act of civil disobedience or just a random act of vandalism isn't known, but it does show a bit of imagination. Rather than just spraying the open flame, which would not have done anything, he throws the entire fire extinguisher in and it inevitably explodes. Russia being Russia he'll probably be tried as a terrorist.

There are many of these inside Russia, this one about 100km outside of Moscow.

Source: OFFNews (Bulgaria)

An 11-year-old Russian blew up the eternal fire in the city of Mozhaisk in the Moscow region, the SHOT telegram channel reported. This was recorded by surveillance cameras, which later identified the miscreant. For the trouble, the boy used a car fire extinguisher.

The eternal fire in the city is located not far from the Home for Children's Creativity on "Zhelyabova" Street. The janitor of the children's facility was on duty when she was startled by a loud explosion from outside. She ran out into the street and saw thick smoke over the quintet of the Eternal Flame in the local park. She immediately called the police. Specialists found in the extinguished fire a powder fire extinguisher with a casing torn by the explosion. The fire extinguisher was of the type that car drivers are required to carry.

A little later it became clear that the memorial was damaged not by a driver, but by an 11-year-old local student in the fifth grade. "As a result of operative and investigative work, the offender was discovered. He turned out to be a local resident, born in 2011," the press center of the police in the Moscow region reported.

As of now, he's being held in a juvenile detention center.