MOSCOW, December 7. /TASS/. Sergey Glazov, the shooter who opened fire in a public service office in Moscow’s southeast Tuesday, is believed to have planned the attack in advance, a source in the law enforcement told TASS.

"Glazov planned the attack in advance; he came to the service office, refused to put a mask on and immediately started shooting," the source said.

A 10-year-old girl was injured in the shooting, but her life is not in danger. She underwent a successful surgery in a hospital, Moscow Deputy Mayor Anastasia Rakova told journalists. Earlier, the media reported that the girl was killed in the shooting.

"A child [was injured], a girl. The surgery has just ended, it was successful," Rakova said, adding that the child and her parents will need psychological aid or counseling.

A source in the law enforcement confirmed that Glazov is an ex-serviceman.

"The detainee is a local resident, and a former serviceman. According to preliminary information, he used a traumatic pistol, modified into a combat one. His neighbors characterized him as a deranged person," the source said.

Chairman of the Investigative Committee of Russian Alexander Bastrykin ordered an operational report on the investigation of the shooting, the agency said on its website.

Investigators and forensic experts are currently working at the scene, determining all circumstances of the incident. The investigation is being coordinated on-site by Moscow Main Investigative Directorate head Andrey Strizhov.

On Tuesday, Glazov opened fire at the Ryazansky public service office after being asked to put on a face mask. According to the latest reports, two people were killed and four were injured. Criminal investigation over charges of murder and illegal possession of firearms has been initiated. Glazov will be subjected to a psychiatric examination.