Jose Samuel Flores Mendoza and Maria Saravia Mendoza were gunned down inside their house in the 700 block of Colonial Drive on Jan. 5, 2013.
Santillan, who was 15 at the time, is on trial in connection with their deaths. Israel Vasquez, who was 16 at the time, is also charged.
On the witness stand Thursday, Moise Reyes said he drove the pair to the duplex where they thought a rival gang member lived. But a year earlier, the Mendozas and their two young sons had moved into the home when the gang member moved out.
Reyes testified Santillan and Vasquez put on masks and gloves before they went into the home so they wouldn't be recognized or leave fingerprints.
"They took a rifle and a handgun," said Reyes, who testified the long gun was an AK-47 assault rifle.
I heard gunshots eventually," said Reyes.
When asked how many, he replied "a lot."
But on cross-examination, Reyes' credibility came into question repeatedly when he admitted he initially told a number of lies to police. Defense attorney Jeff Cutler was at times obviously trying to make it appear to jurors that Reyes may have been one of the gunmen - not his client.
Also on the stand Thursday, a former Wake County Sheriff's Office detective called the killing "very disturbing" and "very emotional."
Ed Welch, who was a veteran investigator at the time of the shooting, detailed for the jury what he saw at the scene.
"It was very disturbing in all honesty," he said. "Something I had never seen before and honestly to learn the facts and circumstances surrounding what had happened. Yeah, very, very emotional."
Welch also testified about searching a home and finding Santillan hiding in the attic. While on the stand, he identified numerous weapons and ammunition found during the search, including the assault rifle and pistol believed to be used to kill the Mendozas.
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The Mendozas' 3-year-old child was also in the home at the time of the killings, but was not hurt. The couple's older child was not at the house.
Some of the most emotional testimony came from neighbors Wednesday who witnessed the aftermath of the shooting through an open door where they said they could see the Mendoza's 3-year old son crying uncontrollably.
"What hit me was the sadness of the child," said Israel Puerta. "He was crying, hugging his father."
Santillan and Vasquez are charged with two counts of murder, felony conspiracy, first-degree burglary, possession of stolen property, and possessing a firearm with an obliterated serial number.
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