A Southern California man was convicted on Monday of killing a family of four - including two young children - with a sledgehammer and burying their bodies in the desert in 2010 over a business dispute.

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 in the bludgeoning deaths of his business associate Joseph McStay, 40, McStay's 43-year-old wife, Summer, and the couple's sons, four-year-old Gianni and three-year-old Joseph Jr.

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

The jury reached its decision on Friday following seven days of deliberations, but it was not announced until Monday.

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Charles 'Chase' Merritt, 62 (pictured in court on Monday), was found guilty of murdering a family of four, the McStays, in 2010

Shaken: Merritt closed his eyes and looked down when the court clerk said the word 'guilty' the first of four times

Prosecutors have said they would seek the death penalty if Merritt, pictured after hearing the jury's verdict, was convicted

Prosecutors say Merritt killed the family with a sledgehammer at a time when he owed McStay $30,000 and was being cut out of the victim's business making and selling custom water fountains, reported KTLA5.

Prosecutors have said they will seek the death penalty - despite California Governor Gavin Newsom's moratorium on capital punishment in the state in March 2019.

Sentencing is scheduled to begin Tuesday.

Prosecutors declined to comment after the verdict, escorting the McStays' relatives from the courthouse.

After the McStay family disappeared, authorities found bowls of uneaten popcorn at their San Diego County home, which had no signs of forced entry, and their car parked at a strip mall near the Mexican border.

Jury convicted Merritt of bludgeoning to death Joseph McStay, McStay's wife, Summer, and the couple's sons, four-year-old Gianni and three-year-old Joseph Jr (pictured together)

In this November 20, 2013, photo, residents of Victorville, California, and surrounding communities place crosses near the graves where the McStay family were buried

For three years, authorities had no idea where the McStays had gone and thought they might have traveled to Mexico

For years, officials couldn't determine what happened to the McStays. At one point, investigators said they believed the family had gone to Mexico voluntarily, though they couldn't say why.

In 2013, their bodies were found in shallow graves in the desert after an off-road motorcyclist discovered skeletal remains in the area. Authorities also unearthed a rusty sledgehammer that they said was used to kill the family.

'It was blow, after blow, after blow to a child's skull,' the Los Angeles Times reported prosecutor Britt Imes said during closing arguments.

Merritt, who worked with McStay in his water features business, was arrested in 2014.

Authorities said they traced Merritt's cellphone to the area of the desert grave sites in the days after the family disappeared and to a call seeking to close McStay's online bookkeeping account.

Merritt also referred to McStay in the past tense in an interview with investigators after the family vanished, and while the evidence linking him to the killings was largely circumstantial, it was 'overwhelmingly convincing,' Imes said.

Police later concluded that the family four, including the young boys, were also bludgeoned to death with a sledgehammer by McStay's business associate, Merritt

Joseph McStay's mother, Susan Blake, center, and other members of the McStay family leave the courthouse after Merritt's guilty verdict

Prosecutors say financial records show Merritt tried to loot the business bank accounts just before and after the family disappeared and backdated checks to February 4, 2010, knowing it was the last day anyone had contact with McStay.

San Bernardino County Supervising Deputy District Attorney Sean Daugherty told jurors at the start of the trial that Merritt wrote checks for more than $21,000 on his dead partner’s online bookkeeping account.

'Greed, and greed’s child, fraud' were the motive, Daugherty argued.

Merritt served time in prison for burglary and receiving stolen property in the 1970s and 80, reported the Los Angeles Times.

In 2001, he pleaded no contest to burglary and grand theft, earning him a six-month stint in jail followed by probation.

Eventually, he was hired by Joseph McStay's company, Earth Inspired Products, to design decorative water fountain, but his troubles continued as he racked gambling debts and more than $20,000 in unpaid taxes, according to court documents.