SAN DIEGO — A Southern California man was convicted Monday of bludgeoning a couple and their two little boys to death, then burying their bodies in a remote desert area where the crime remained hidden until an off-roader stumbled across skeletal remains.

After a trial that spanned more than four months and depended largely on circumstantial evidence, jurors in San Bernardino found 62-year-old Charles "Chase" Merritt guilty of the first-degree murders of business associate Joseph McStay, McStay's wife, Summer, and the couple's 3- and 4-year-old sons.

Merritt closed his eyes and looked down when the court clerk said the word "guilty" the first of four times. Sobs came from the packed courtroom. Someone called out, "Yes!"

Prosecutors said Merritt killed the family with a sledgehammer at a time when he owed McStay money and was being cut out of the victim's business making and selling custom water fountains.

The jury also found the special circumstance of multiple murders.

The judge scheduled the penalty phase to begin Tuesday. Prosecutors have said they will seek the death penalty.

Prosecutors declined to comment after the verdict, and families on both sides left without speaking to reporters.

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The McStay family vanished in 2010

When the McStay family disappeared there was no evidence of struggle or foul play in their Fallbrook home, but there were signs of a hasty departure – unopened groceries left on the counter and the family's dogs still in the backyard.

Four days after their disappearance, the McStay’s Isuzu Trooper was located near the San Ysidro border.

Grainy surveillance video of a family of four crossing the border on foot and Google inquiries found on the family's home computer researching documents required for travel to Mexico, initially led the focus of the search south of the border – leading to speculation that the McStays may have left voluntarily.

More than three years later, though, in November 2013, a motorcyclist found the remains of the McStay bodies buried in shallow graves in the Mojave Desert near Victorville.

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A sledge hammer was also found in one of the graves.

Investigators ruled the deaths a homicide and determined that the McStays were fatally bludgeoned inside their Fallbrook home, although no trace of blood was ever found there.

In 2014, Merritt, was arrested for the murders. He went on trial in January of this year.

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Prosecutors said Merritt killed the McStays over money after he was being cut out of the decorative fountain business the two owned. Prosecutors also said Merritt had stolen $42,000 from the business – which Joseph McStay had discovered. They claim surveillance video and cell phone evidence link him to the crime. 

“That greed and self-interest motivated a man to kill a family of four and take them from this earth,” the prosecution said during trial.

RELATED: Prosecutor: Man's greed drove him to kill McStay family

Merritt's attorneys said the two men were best friends and investigators overlooked another possible suspect in the killings. Instead, they said, authorities zeroed in on an innocent man, but the evidence didn't add up, noting there were no signs of an attack inside the family's home.

"They tried his character and not the facts of this case," defense attorney James McGee told jurors.

Many questions still remain about the family's disappearance. Prosecutors acknowledge details of the killings aren't entirely clear but say the evidence from the family's car, cellphone towers and financial accounts link Merritt to the killings.