Joy Deleston was a no-nonsense Gwinnett deputy who moonlighted as an actress and parented three children, all with a smile on her face.

That's why no one who knew the charismatic 39-year-old can comprehend what police say: that Deleston's 17-year-old son gunned her down Thursday along with her two young daughters at their Lawrenceville home.

Gwinnett Sheriff's Office (ENLARGE)

Anthony Tyrone Terrell, 17, has been charged with three counts of murder.

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Police say the teenager, Anthony Tyrone Terrell, implicated himself in the slayings and even told investigators where he disposed of the gun. They still don't know why he did it.

"We do not have a motive at this time," said Officer David Schiralli, spokesman for the Gwinnett County Sheriff's Department.

While Terrell sat Friday in the DeKalb County Jail, the classrooms and hallways of Central Gwinnett High School, where Terrell is a sophomore, were buzzing with word of the shooting. Terrell is charged with three counts of murder and three counts of aggravated assault.

Lewis Colquhoun, a freshman, said Terrell lives down the street from him and is "just chill," a cool guy. He and other classmates said they don't believe Terrell killed his mother and sisters.

"Everytime he talks about his mom, it's something good about her," Colquhoun said. "I don't think it's true. I don't believe it at all. He's not the kind of kid to snap."

Robert "IronE" Singleton, a writer, director and actor from Atlanta, acted in several movies with Deleston and knew her family. He last talked to Terrell at a November film premiere.

Terrell "was a good kid. That's the reason why it's so disturbing, because you just didn't see that coming," Singleton said. "He seemed very humble. He was respectful."

Friends also said he loved his sisters. Jelani, 4, was the daughter of rap star Juvenile, according to child-support records in Gwinnett County. The rapper, whose real name is Terius Gray, could not be reached for comment on Friday.

Micaiah, 11, was a sixth-grader at Richards Middle School, said Sloan Roach, spokeswoman for Gwinnett County schools.

Officers responding to reports of gunshots fired in the Madison Chase subdivision off Simonton Road in Lawrenceville found the bodies about 8 p.m. Thursday. After finding a bullet hole in the house next door, officers walked over to the traditional-style, two-story house at 415 Madison Chase Drive to check on the residents' welfare.

Inside the front door, police found Deleston and Micaiah lying dead on the floor. Upstairs, they found Jelani's tiny body.

"It was a tragic scene, a very horrific scene seeing small children like that being gunned down," Schiralli said.

Deleston, an actress who appeared in locally produced films, was also a 7 1/2 year veteran of the Gwinnett County Sheriff's Office. She previously worked for the Lowndes County Sheriff's Office in South Georgia.

Deleston worked in the sex-crimes unit of the sheriff's office and interacted with registered sex offenders, maintaining a database of their addresses in Gwinnett.

On Friday, the tight-knit community of officers at the jail were still coming to terms with the killings, said Sgt. Jeremy Brown, her supervisor. "It may set in in a couple of days," he said.

Deleston would often bring him breakfast at work in the morning, unprompted, Brown said.

"I actually had to ask her to stop," he said. "That was the kind of person she was."

Gwinnett Sheriff Butch Conway issued a statement Friday calling the shootings "totally senseless and cowardly."

"It is heartbreaking to lose someone in the way that we lost her. I am very angry that these three lives were so violently taken from us," Conway said.

Robinson Vil said Deleston was a supporting actress in three films for his Atlanta-based production company, Villain Pictures: "The Effect," "Riff" and "Dark Secrets." He met Deleston when she auditioned for a role in 2004 and immediately fell in love with her personality. Vil wrote parts for her in all his subsequent movies, which she happily took even though Vil couldn't afford to pay the actors.

"I told her, wherever this goes, you're coming with me," Vil said. "She was a very good actress. So now with this happening, it's just like a big blow."

One neighbor, Jim Clark, who lives near the deputy's house, said he didn't really know Deleston's family, but he was "shocked and horrified" to learn of the crime.

He said the deputy and her family had been living there for about a year. Clark's family was happy when he learned a law enforcement officer was going to be their neighbor.

"We were excited about it," Clark said. "It's good to have a sheriff's car on your street."

It was not known whether there were any warning signs of violent tendencies in Terrell. He turned 17 in January, and if he had a criminal record before this year, it would be sealed because he was a juvenile, said Gwinnett police spokeswoman Cpl. Illana Spellman.

Dr. Elissa Benedek, a psychiatrist in Ann Arbor, Mich., who specializes in juvenile violence, said there could be any number of reasons behind the slayings.

"The research on this area suggests that some of the children are seriously mentally ill, a very small percentage of them," Benedek said. "A larger percentage are reacting to family dysfunction, and a very small percentage have personality problems."

Defense attorney Lyle Porter is assigned to represent Terrell, but he declined to comment on the case Friday. Terrell waived a first appearance Friday. He is expected to appear in court for a probable cause hearing some time next week.

Staff writers Mike Morris, Steve Visser and Tim Eberly contributed to this article.