DOUGLASVILLE, Ga. (AP/The Huffington Post) -- Authorities in west Georgia say a 14-year-old is in custody after his 77-year-old great-grandmother was stabbed to death with a sword and his grandmother was wounded.

Douglas County Sheriff Phil Miller says officers arrived at the home Monday afternoon and found the grandmother, who is in her 50s, barricaded inside a room and the great-grandmother on the ground outside.

They say the teen was standing in the doorway with what they described as a full-sized sword and a pellet rifle, and that he shot out the windows of a patrol car.

Authorities say police used a stun gun to take the teen into custody after a standoff. The grandmother was taken to a hospital for treatment of what officials described as non-life threatening injuries.

Relatives of the suspect told CBS Atlanta that the teen -- identified by the station as a 15-year-old -- attacked his great-grandmother and grandmother when he was told to stop playing video games.

Investigators say this is the third time this year that they have responded to calls about the teen behaving violently.

"We've arrested him on two different occasions," Miller said, according to CBS Atlanta. "Once in June where he had another sword, which is in evidence. This is not the same sword. He cut his grandmother on the foot with it that time."