GYUMRI, Armenia -- Investigators in Armenia say a Russian soldier is suspected of killing six members of a family in Gyumri, a city that hosts a Russian military base.

The Armenian state Investigative Committee said the victims -- a couple, their son and daughter-in-law, a 2-year-old granddaughter, and an unmarried daughter -- were found shot dead in their house on January 12.

The couple's six-month-old grandson was hospitalized in a grave condition.

Investigators said victims were shot with an AK-47.

Investigative Committee officials said the suspect, Valery Permyakov, illegally left his unit in the morning. They said military boots with his initials had been found at the scene of the crime.

Russia has about 3,000 troops at the 102nd iilitary Base in Gyumri, one of Russia's largest military installations abroad.

Armenia is a member of the Collective Security Treaty Organization (CSTO) and the Eurasian Economic Union, two Russian-dominated groups of former Soviet republics.

Russian authorities said a Russian Defense Ministry commission led by First Deputy Defense Minister General Arkady Bakhin would join the investigation. The commission vowed that "all those guilty will be brough to justice."

With reporting by Interfax