Santillan, who was 15 at the time, is on trial in connection with the deaths of Jose Samuel Flores Mendoza and Maria Saravia Mendoza, who were gunned down inside their house in the 700 block of Colonial Drive near Garner on Jan. 5, 2013.
On the witness stand Friday, yet another veteran investigator called the crime scene - where a couple was killed in a case of mistaken identity - among the worst he's ever seen.
"It's probably one of the most horrific scenes I've been on in my career in public service," Wake County Sheriff's Investigator Ed Blomgren said. "I've worked in EMS, fire, military, and now law enforcement. And it ranks right up there with one of the most horrific."
He also told jurors about ammunition he found at the home where Santillan was arrested. Blomgren said stamps on bullets had been scratched off - matching shell casings found at the duplex.
On the witness stand Thursday, Moise Reyes said he drove Santillan and Israel Vasquez - who was 16 at the time and also charged - to the home where the Mendozas and their two young sons had moved when the teen's rival gang member moved out. 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.
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.
RELATED: Autopsy: Wife in Garner murders shot 7 times
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.
Report a Typo