SAN BERNARDINO, Calif. — A business associate was arrested in the murders of a family of four, including two young boys, whose disappearance from their San Diego County home in 2010 was a mystery until their remains were discovered in graves in the California desert last year, officials said Friday.

San Bernardino County Sheriff John McMahon identified the suspect as Charles Merritt, who was due in court later in the day to face four counts of murder.

The lengthy investigation revealed that Joseph and Summer McStay and their two young sons were killed in their home in Fallbrook and all were victims of blunt-force trauma, the sheriff said.

Joseph McStay had a business designing and installing home water features. Investigators said he had asked Merritt to design some special waterfalls and the two met at a restaurant on the day the family is believed to have been killed.

Merritt’s name surfaced previously in the investigation. In 2011 it was reported that Joseph McStay’s last cellphone conversation was with Merritt.

The couple and their boys, ages 3 and 4, vanished in February 2010 from Fallbrook.

A year ago, their skeletons were found in the desert outside Victorville. The site was not far from heavily traveled Interstate 15, which connects San Diego and Las Vegas.

Investigators said there were no signs of forced entry at the family’s home or in their SUV, which was found parked near the US-Mexico border.

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When they were reported missing, authorities went to the house and found eggs that had rotted on the kitchen counter and two pet dogs in the backyard, indicating the family hadn’t prepared for an extended leave.

Nothing was missing from the home, and the couple’s credit cards and tens of thousands of dollars in bank accounts never were touched.