MARIETTA, Ga. -

One day after a 15-year-old testified that his co-defendant -- 18-year-old De'Marquise Elkins -- shot a toddler in a stroller while attempting to rob the the boy's mother, prosecutors played a video of the younger teen reenacting what happened on that Brunswick street the morning of March 21.

Elkins is on trial for murder in the shooting death of 13-month-old Antonio Santiago on March 21.

In the video played for the jury Friday, Dominique Lang described to Glynn County Police Detective Roderic Nohilly how the shooting went down at the corner of London and Ellis streets.

"He was, like, 'Give me the purse,' and she was, like, 'No, no. What are you doing? I got a baby.' And then he slapped her with the gun," Lang is heard saying.

Lang tells officers he saw Elkins threaten West and her baby and ultimately fire shots -- saying the first one hit the ground, the second struck the mother's leg. Lang says he was running away when the third shot was fired that hit the toddler in the head. 

"I asked him, 'Did you shoot the baby?' and he was, like, 'No.' So I was, like, 'OK,'" Lang said.

Lang says they ran to his grandmother's home, where he gave his aunt, Debra Obley, $5 to take Elkins to a relative's home.

"Are you sorry for what you did?" the detective asked.

Nodding his head, Lang replies, "I couldn't sleep at night. I wish I never went with him."

Lang was charged with murder as an accomplice, and will be tried at a later date.

Brunswick detective Roderic Nohilly also testified Friday. He said Elkins (pictured, right) told investigators that he woke up at 10 a.m. that morning and left the house at 11 a.m., but surveillance video showed a person they believe to be Elkins wearing a red shirt at the scene about about 9 a.m.

During cross-examination, the defense pointed out that Lang's testimony had Elkins wearing a black shirt that morning.

After officers got an arrest warrant and were taking Elkins into custody, he made what Nohilly described as a "spontaneous utterance."

"He said, ‘Y’all ain’t got (expletive) on me. Y’all ain’t got no gun. Y’all ain’t got no fingerprints. All y’all got is a (expletive) acquittal,'" Nohilly testified.

Tim Pulliam Tweets From Courtroom

However, when Elkins saw another detective smile at his outburst, the defendant said to police, "Oh, got the gun?"

Prosecutors said information from Elkins' mother and sister led investigators to a pond where they found a .22-caliber revolver. Elkins' mother, Karimah Elkins, is standing trial alongside her son on charges of evidence tampering and lying to police. Elkins' sister also was charged with evidence tampering, but will be tried seperately.

The state also called officers to the stand Friday to prove Karimah Elkins gave false statements to police.

An officer testified that she told them Elkin's was with her at the time of the shooting, but a corrections officer testified that she had just been released from jail and hour and half after the shooting.

Late Friday, the issue of gunshot residue found on the toddler's parents was argued before the jury.

A forensic scientist with the Georgia Bureau of Investigation crime lab testified that a small amount of gunshot residue was found on Antonio Santiago's father, Louis. The scientist also said the child's mother, Sherry West, had more gunshot residue on her.

The witness told jurors the residue can easily transfer from person to person by touching a gunshot wound, or if they are close to a fired gun.

The defense claims Elkins did not test positive for gunshot residue after the shooting -- although he was not tested until the next day.

Forensic scientist Sarah Peppers says that while gunshot residue could stay on a person indefinitely, with normal washing, it can disappear within eight hours.

West is expected to testify for the prosecution early next week.  Louis Santiago is on the witness list for the defense.

The trial recessed for the weekend after the jury was reminded not to watch or read any coverage of the trial or discuss the case with anyone.  They are not sequestered.

The killing drew national attention, and the trial was moved to the Atlanta suburb of Marietta owing to extensive publicity. Elkins faces life in prison if convicted of murder. At the time of the shooting he was 17, too young to face the death penalty if convicted under Georgia law.