The story of the McStay family disappearance began on a quiet street in Fallbrook, California, on Avocado Vista Lane. Joseph McStay, a successful owner of a custom water feature business, his wife Summer, and their two young sons, Gianni and Joseph Jr., were living the American Dream in their new home. Then, on February 4, 2010, the dream dissolved into a nightmare when the entire family vanished.

When police arrived at the home for a welfare check, the scene suggested a family that had simply stepped out for a moment. Perishable food was left on the kitchen counter, and two half-eaten bowls of popcorn sat in front of the television, a testament to a life abruptly interrupted. There were no signs of forced entry, no blood, and no signs of a struggle. Yet, one critical detail raised the first true red flag: the family’s two beloved dogs were left alone in the backyard, unfed and without water. For a couple described by all accounts as loving and responsible pet owners, this abandonment was “completely out of character.”

Joseph’s brother, Michael McStay, filed a missing person’s report 11 days after the family was last heard from. The ensuing investigation by the San Diego County Sheriff’s Office would quickly become one of the most perplexing missing persons cases in memory.

The Mexican Theory: A Case of Voluntary Flight

The initial direction of the investigation was dictated by two pieces of evidence that pointed definitively south. First, the family’s white Isuzu Trooper was found four days after their disappearance in a parking lot just a block and a half from the US-Mexico border in San Ysidro. Second, a forensic search of the family’s computer revealed multiple inquiries on “crossing into the Mexico area with children and what’s required for passports.”

Adding to this, surveillance footage from the border crossing captured what appeared to be a family of four—two adults and two small children—calmly walking across the border on the same day the car was towed. Faced with what looked like an orchestrated getaway, and with no evidence of foul play in the home, investigators concluded the McStays had likely fled to Mexico voluntarily.

This theory, however, never sat right with those closest to the family. Joseph’s brother, Michael, pointed to crucial items left behind that contradicted the idea of a planned departure, including Joseph’s surfboards and, more significantly, the double stroller the parents used for their two young boys. “They don’t go anywhere without the double stroller,” he stated, expressing the doubts that the family was forced to suppress for years. Meanwhile, Joseph’s friends noticed something else—financial irregularities. Joseph’s business partner, Gina Watson, found withdrawals from the company’s PayPal account totaling almost $7,000, all withdrawn before the McStays were even reported missing. While the financial activity was initially dismissed as Dan Kavanaaugh, Joseph’s web designer, trying to keep the business afloat, the doubts about the “voluntary” narrative persisted.

A Grim Discovery Changes Everything

The true answer to the McStay mystery lay not in Mexico, but 100 miles north of their Fallbrook home, in the desolate, high desert of Victorville, California.

On Veterans Day, 2013—nearly four years after the family vanished—a dirt biker riding off-road stumbled upon what he initially mistook for an upside-down tortoise shell. It was a small human skull. Following the 911 call, investigators from the San Bernardino Sheriff’s Office were dispatched to the desolate area, eventually locating two shallow graves, just under two feet deep. The careful excavation revealed not one, but four victims. Dental records and later DNA testing confirmed the tragic truth: the remains belonged to Joseph, Summer, Gianni, and Joseph Jr. McStay.

With the recovery of the bodies, the missing person’s case instantly became a quadruple murder investigation. The focus shifted from where the family went to who killed them. The evidence recovered from the graves was immediate and grim:

The Murder Weapon: A Stanley sledgehammer was discovered underneath the victims, its size “consistent with the impact marks” found on the remains.
The Restraints: Joseph’s body showed evidence of “blunt force trauma to his head,” and an extension cord was tied around his neck, binding him to his lower extremities.
The Vehicle: An incredible clue, baked into the desert ground by years of sun and rain, were clear tire impressions that indicated a single car had backed up to the gravesite.

San Bernardino detectives now had to work backward, examining the old San Diego case file with a fresh, homicide-oriented perspective.

The Last Man Standing: Chase Merritt

The investigators quickly turned their attention to two business associates who had known Joseph best: web designer Dan Kavanaaugh and Joseph’s custom fabricator/welder, Charles “Chase” Merritt. Kavanaaugh had a strained relationship with Joseph over money, including threatening to shut down Joseph’s website if he wasn’t paid. However, Kavanaaugh quickly produced a verifiable alibi: he was in Hawaii at the time of the disappearance, a fact corroborated by his girlfriend’s testimony and his own plane ticket.

This left Chase Merritt. Merritt was the last confirmed person to have seen Joseph alive, meeting him for lunch on February 4, 2010. While initially presenting as a concerned friend and business associate who was willing to help the police find Joseph, detectives began to uncover the truth behind their working relationship.

The motive was financial greed. Investigators found that Merritt was deeply in debt to Joseph, owing him a shocking amount of money—$42,000—three days before the family vanished. Coupled with a confessed gambling problem where he would “go to casinos and spend a lot of money,” the financial burden created a clear motive for murder. Furthermore, Merritt, who grew up in the high desert, was intimately familiar with the remote area where the bodies were found.

The Irrefutable Digital Trail

The case against Merritt solidified with two pieces of irrefutable forensic evidence that destroyed his fabricated alibi:

The DNA: San Diego investigators had collected DNA swabs from the family’s Isuzu Trooper. When re-examined, trace DNA found on the steering wheel and the gear shift matched Chase Merritt. This directly contradicted Merritt’s initial statement to police where he denied ever driving the vehicle. Investigators concluded Merritt had been the one who drove the car down to the San Ysidro border to plant the false trail to Mexico.
The Cell Phone Ping: The most damning evidence came from Merritt’s own cell phone records. Two days after the McStays were murdered, Merritt’s phone connected with a cell phone tower in Victorville, California. That tower oversaw the very area where the two shallow graves were later discovered. When confronted, Merritt frantically denied being in the area, claiming the records must be wrong, yet the evidence was definitive: the phone ping placed him at the burial site.

The Verdict and Sentencing

In 2019, nine years after the McStays vanished, Chase Merritt stood trial for four counts of first-degree murder.

The defense, led by his attorney, tried to create reasonable doubt by shifting blame to Dan Kavanaaugh and by arguing that the DNA in the car was merely secondary transfer. They even called a forensic video expert who testified that the surveillance footage of a truck leaving the McStay home could not be conclusively identified as Merritt’s vehicle. The defense’s efforts, however, were overwhelmed by the weight of the digital and forensic evidence, especially the cell phone ping.

The prosecution also highlighted Merritt’s own words. When talking to an interviewer, he stated, “I’m definitely the last person he saw,” a chilling confirmation of his opportunity.

After a nearly nine-week trial, the jury deliberated for six long days. On June 10, 2019, the jury returned a verdict of guilty on all four counts of first-degree murder.

The verdict brought a tragic but necessary finality for the McStay family’s loved ones. In 2020, Chase Merritt was sentenced to death. The conviction finally closed one of the most baffling cold cases in California history, revealing the true face of the killer: not an international criminal, but a business partner who chose greed and violence over friendship, ending the lives of an entire family to cover a debt.

The family’s remains were ultimately buried in Orange County, California, their memory now permanently tied to the beach where they once enjoyed their simple, beautiful life.