SAN BERNARDINO (CBSLA/AP) — A 62-year-old man was found guilty Monday in a San Bernardino courtroom of murdering a Northern San Diego County family of four more than nine years ago and burying their bodies in shallow graves near Victorville.

Charles “Chase” Merritt could face the death penalty at sentencing. The jurors’ decision came after about a week of deliberations.

The McStay couple and their two young sons vanished suddenly in February 2010 from the Fallbrook home, with bowls of popcorn left uneaten in their house and no sign an attacker forced their way inside.

In November 2013, their bodies were found by an off-road motorcyclist about 100 miles away, in shallow desert graves in a desert area just north of Victorville in San Bernardino County. Along with the bodies was a rusty sledgehammer.

Merritt was arrested in November of 2014.

On Friday, a jury reached their verdict in the murder case against Merritt, who authorities say killed the family with a sledgehammer after his business associate, 40-year-old Joseph McStay, tried to cut him out of a business making and selling custom water fountains.

While many questions remain about the killings, prosecutors argued that evidence from the family’s car, financial accounts and cellphone towers linked Merritt to the deaths of Joseph McStay, his wife, 43-year-old Summer McStay, and the couple’s sons, 4-year-old Gianni and 3-year-old Joseph Jr.

The San Bernardino County coroner’s office ruled the causes of death to be blunt force trauma to the head. Officials said Gianni suffered at least seven blows in the incident.

After the McStays disappeared from their home in San Diego County, investigators couldn’t immediately determine what had happened. Their car was found parked at a strip mall near the Mexican border, and at one point, investigators said they believed the family had gone to Mexico.

Merritt’s attorneys said Merritt and Joseph were best friends and investigators overlooked another possible suspect. They said the evidence doesn’t add up, noting there were no signs of an attack inside the family’s house.

According to the San Bernardino County Sheriff’s Department, a preliminary investigation revealed Joseph had lent Merritt money to cover a gambling debt prior to the family’s disappearance. Merritt reportedly owed over $30,000 to McStay along with more than $20,000 in back taxes.

Authorities said they traced Merritt’s cellphone to the area of the desert gravesites in the days after the family disappeared and to a call seeking to close McStay’s online bookkeeping account. They also said Merritt referred to McStay in the past tense in an interview with investigators after the family vanished.

Prosecutors have said they will seek the death penalty.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)