The 15-year-old accused of killing his great-grandmother and injuring his grandmother in a samurai sword attack will have a mental evaluation before the case proceeds, Channel 2 Action News reported.

Gevin Allen Prince of Douglasville faces murder and aggravated assault charges in the Aug. 15 attacks that killed Mary Joan Gibbs, 77, and left his grandmother, Laura Prince, seriously injured.

The prosecution and the defense agreed to Gevin Prince's mental evaluation during a hearing in Douglas County Superior Court on Wednesday.

"We think competency is an issue in the case," his attorney, Travis Glahn, told Channel 2. "We don't think he fully understands what's going on. This is someone who is being charged as an adult with a pretty serious crime who is barely 15 years of age."

The incident began as a disagreement over a home computer, Laura Prince previously told the AJC. She said Gevin reached for a sword, attacked her and killed her mother, who was found dead in the yard of the Spring Ridge Drive home when police arrived. Gevin Prince had a sword and a BB gun, which he used to fire at deputies and hit patrol cars before being Tasered and arrested, police said.

"There's no doubt he has issues," Douglas County District Attorney David McDade told Channel 2. "But a lot of people who do a lot of violent crimes have issues, [but that] doesn't mean they are going to escape criminal responsibility for what they did."

The results of the mental evaluation are expected to be released Jan. 11, the report said.

In court Wednesday, Laura Prince still had a cast on her arm that was slashed and broken during the attack, Channel 2 noted.

She does not want her grandson tried as an adult, but her brother, David Cook, does.

"He butchered my mother with a sword," Cook told Channel 2.

Laura Prince previously told the AJC that she had raised Gevin and had tried to get help for his mental problems. Gevin has Asperger's syndrome, which is similar to autism, and the older he got, the more he “acted out” physically, she said.

Cook said that he and his sister have not spoken since the killing.

--Staff writer Alexis Stevens contributed to this article.