LAWRENCEVILLE, Ga. -- Mourners are still coming to grips with the loss of slain Gwinnett County Deputy Joy Deleston and her young daughters. A memorial service was held Sunday.

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. He is scheduled to be in court this week for a probable cause hearing after waiving his first appearance.

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Terrell is a junior at Central Gwinnett High School. Jelani is the daughter of rap star Juvenile, according to child support records in Gwinnett County. The rapper's real name is Terius Gray.

He was charged with three counts of murder and three counts of aggravated assault. He is being held without bond.

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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.

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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.

Deleston worked in the sex crimes unit, according to Schiralli.

"It is heartbreaking to lose someone in the way that we lost her," said Gwinett County Sheriff Butch Conway. "I am very angry that these three lives were so violently taken from us in a totally senseless and cowardly act."

Terrell arrived at the house while investigators were there and they took him into custody.

Neighbors in the Madison Chase subdivision said the family moved in less than a year ago. They often saw Deleston in her squad car coming home from work and said having a deputy in the neighborhood was reassuring.

Jeff Beaird has lived across the street for about three years. He says he often saw Terrell in the driveway shooting hoops with friends or washing his mother's patrol car.

Beaird says it's shocking because "you don't expect something like this to happen."