Authorities announced Friday that they have charged the victim's twin daughters, Jasmiyah and Tasmiyah Whitehead, and said that the 16-year-olds will be tried as adults. Both are being held at the Rockdale County Jail.

Jarmecca Whitehead, 34, was stabbed to death in January on Appaloosa Way in the Bridle Ridge Walk subdivision in Conyers, police said.

VIDEO: Twins Charged In Mother's Slaying | SLIDESHOW: Mother Found Murdered In Conyers

At the time, Whitehead's daughters told police that they discovered their mother’s body when they got home from school. The family lived in a gated community.

Police said they were waiting on results from the Georgia Bureau of Investigation crime lab, and early Friday morning they arrested the twins, one at Tucker high school, the other at a relative's home in Clarkston.

Conyers Police Chief Gene Wilson said he still can't understand why this happened.

"I really don't know. It was a brutal murder. She was stabbed and beaten to death, and as far as the motive, I just don't know," said Wilson.