BRUNSWICK, Ga. -

Detectives testified at a pretrial hearing Friday that 15-year-old Dominque Lang confessed to being present when 13-month-old Antonio Santiago (pictured, below) was shot and killed in March, but says he was not the shooter.

Detectives said Lang told them a "kid named Marquise" was there, and he gave the a re-enactment consistent with Sherry West's, the baby's mother, who was pushing him in a stroller when he was killed.

De'Marquise Elkins, 17, and Lang are both charged with murder in the killing. The trial for Elkins (pictured at bottom of story), his mother and sister is set to begin Aug. 19 in Cobb County. A separate trial will be held for Lang, but there's no word on when that will be.

Detectives testified that Lang's aunt gave the teens a ride shortly after the killing and said she knew Lang's friend to be an Elkins boy, the son of Karimah Elkins, who's also charged in the case. She said he was ducking and acting odd while in her car.

"Whoever killed this child, and I was like, 'Wow, somebody actually had the nerve to shoot a baby in the face? Just to kill a baby, it's not human,'" said Algrey Brooks, who tipped off police.

De'Marquise Elkins in court Detectives said Brooks is now in jail on unrelated charges but played a big part in the arrests of the two teens. He said he was living with Lang's aunt at the time, and after the shooting took place that Thursday morning, she made a revelation.

"She said I believe I know who did this," Brooks said.

He said he took that information to police after hearing a reward was being offered. Detectives said Lang's aunt, Deborah Obley, is the one who led them to the 15-year-old suspect and told them she gave him and another teen a ride after the shooting. Prosecutors said that other teen was Elkins.

Elkins was arrested without incident. Detectives said he had two .22 caliber bullets in his pocket.

Elkins' defense attorneys have raised questions about the child's parents, Sherry West and Louis Santiago, pointing out both of them tested positive for gunshot residue, while Elkins did not. The baby's father gave an explanation, saying it must have rubbed off from West's wound.

"I just saw the bullet hole," he said. "I saw the bullet hole for the first time. I touched it like a little kid. I've never had a gun in my life."