A former serviceman opened fire in a public service office in Moscow after he was asked to put on a face mask, the Moscow police reported on Tuesday.
Two people were killed and four wounded in the shooting, including a 10-year-old girl, the police said in a statement.
The shooter, identified as Sergey Glazov, was arrested at the spot by a migration police officer.
Glazov was in a deranged condition while committing the crimes and he will be sent for a psychiatric examination, the police noted.
Also armed with a knife, he was shooting with an unregistered military weapon, they added.
The Russian Investigative Committee has opened a criminal case under articles on murder and illegal arms trafficking.
Moscow Mayor Sergei Sobyanin expressed his condolences to the families of the victims.
