A 17-year-old was arrested Friday in the murder of his mother, a Gwinnett County sheriff's deputy, and his two sisters.

Anthony Tyrone Terrell is charged with killing his mother, Joy Deleston, and his sisters Micaiah, 11, and Jelani, 4.

Police spokeswoman Corporal Illana Spellman said the motive for the killings is still under investigation. Terrell was taken to jail in neighboring DeKalb County to avoid any potential conflict because Deleston worked for Gwinnett County, Spellman said. He is being held without bail.

Spellman said she could not confirm whether Deleston's service weapon was used in the fatal shootings or if investigators recovered the gun used in the killings. She said she did not know if there were any prior police calls to the home. A neighbor called police Thursday night when she heard gunshots and a bullet came through the wall of her house.

Officers who responded realized the bullet came from the deputy's house at 415 Madison Chase Drive and saw the deputy's marked patrol vehicle in the driveway, said Gwinnett County police spokesman David Schiralli. When they investigated they found the bodies of the deputy and her daughters.

"They knew a deputy lived there, so they knocked at the door to see if everybody was all right," Schiralli said. "There was no answer, but lights were on. They opened the door a little bit to announce themselves. That's when they saw the 11-year-old."

She was just inside the front door. The deputy's body was further inside the house. The 4-year-old was discovered in an upstairs bedroom. [READ MORE]