A Douglasville teen admitted to stabbing his great-grandmother to death with a samurai sword.

Channel 2’s Dave Huddleston was in court when 16-year-old Gevin Prince pleaded guilty but mentally ill Wednesday. His attorney previously said the teen has Asperger's syndrome.

The stabbing happened at the family’s home in August 2011. Deputies said Prince was upset over a video game. Investigators said he used a 34- to 36-inch sword to cut his grandmother, Laura Prince, in the arm and to kill his great-grandmother, 77-year-old Mary Joan Gibbs.

The attack marked the third time deputies have encountered the teen. Sheriff Phil Miller said on two previous occasions, the teen was sent to a hospital to be mentally evaluated and then turned over to Juvenile Justice. But both times, Miller said, the boy was released, despite his violent history.

Prince received a life sentence in prison, plus 30 years.