TL;DR: Phone data showed Jonathan Gerrish, Ellen Chung, their 1-year-old daughter and dog died from environmental exposure after running out of water on an 8-mile Sierra National Forest hike in 42°C heat.

What happened on the Savage Lundy trail

Jonathan Gerrish, 45, Ellen Chung, 31, their one-year-old daughter Aurelia Miju Chung-Gerrish and their eight-year-old dog Oski set out on an eight-mile hike through California's Sierra National Forest, where temperatures reached 42°C, according to the Irish Mirror.

All four were found dead on a remote hiking trail on August 18, 2022, according to the Irish Mirror.

The bodies were located on the Savage Lundy and Hite's Cove trails, according to the summary published by Particle.

Investigators with the Mariposa County Sheriff's Office, assisted by the FBI, later closed the case with a coroner's determination of environmental exposure due to lack of water and shelter, according to Particle.

The Mariposa County Sheriff's Office issued statements backing the coroner's determination that the family died from environmental exposure, according to LancsLive.

In October of that year, Sheriff Jeremy Briese described what occurred as "an unfortunate and tragic event due to the weather," according to LancsLive.

The final phone record

There was no mobile reception where the family was discovered, but records showed Jonathan Gerrish had tried to send multiple text messages, according to the Irish Mirror.

One unsent attempt read: "Can you help us," according to the Irish Mirror.

Another attempted message stated: "On savage lundy trail heading back to Hites cove trail. No water or ver [over] heating with baby," according to LancsLive.

Jonathan Gerrish also tried to make five phone calls, none of which were to emergency services, according to the Irish Mirror.

Data extracted from the father's phone showed multiple failed call attempts and desperate texts including a message saying they had no water and were overheating with the baby, according to Particle.

Photos recovered from the phone showed the family left for the walk at 7.45am, with the final image of a creek taken at around 12pm, according to the Irish Mirror.

Images retrieved from the phone revealed the family began their walk at 7.45am, with the last photograph of a creek captured at approximately 12pm, according to the account published by the Daily Express US.

The cell-phone data results were described by Sheriff Jeremy Briese as the last piece awaited by relatives and detectives, according to LancsLive.

Briese said the extracted information confirmed initial findings, according to LancsLive.

Briese added: "I am very proud of my team and our partner agencies for all the work they put in. Their dedication has allowed us to close this case and answer lingering questions the family had, bringing them a little peace," according to the Irish Mirror.

How search teams found them

The family's babysitter raised the alarm two days before they were found when she arrived to care for their daughter and found no one at home, according to the Irish Mirror.

She contacted their family members, who then reported the three missing that night, according to the Irish Mirror.

Search and rescue teams first found the family's car, but were initially baffled at the cause of death when they found their bodies, according to the Irish Mirror.

The babysitter noted the house empty and search teams later found the car before locating the bodies on the Savage Lundy and Hite's Cove trails on August 18, 2022, according to Particle.

Mariposa County Sheriff Jeremy Briese said: "When we located the family there were no apparent causes of death," according to LancsLive.

Mariposa County Sheriff's spokeswoman Kristie Mitchell said: "Coming across a scene where everyone involved, including the family dog that is deceased, that is not a typical thing that we have seen or other agencies have seen. That is why we're treating it as a hazmat situation. We just don't know," according to LancsLive.

Briese said: "I've been here for 20 years and I've never seen a death, with any case, like this. There are no obvious indicators of how it occurred . . . you have two healthy adults, you have a healthy child and what appeared to be a healthy canine all within a general same area, deceased," according to the Daily Express US.

Ellen Chung's body was found further up the trail and it appeared as though they had all sat down in the sun, according to Strange Outdoors as cited by the Irish Mirror.

The family had completed most of the hike before they died, according to the Irish Mirror.

Jonathan Gerrish, originally from Lancashire, had relocated to the United States to work for Google, according to the Daily Express US.

What was found with them

Investigators reported one empty water bladder backpack was found with the bodies alongside some snacks and baby formula, but they had no other water containers with them, according to the Irish Mirror.

Scene evidence included one empty hydration bladder and baby formula, according to Particle.

Two months later, after autopsies and extensive investigations, investigators concluded the family had run out of water and shelter, according to the Irish Mirror.

Cell-phone data and scene forensics showed the family ran out of water and could not find shelter, which led investigators to close the case, according to Particle.

Causes investigators ruled out

Multiple potential causes were examined with assistance from the FBI, according to Particle.

Investigators, assisted by the FBI, tested for poisons, carbon monoxide, lightning, drugs and other causes and reported no evidence supporting those alternatives, according to Particle.

Multiple causes of death were ruled out during the investigation including suicide, being caused by a gun or other weapon, alcohol, illegal drugs, a lightning strike and exposure to cyanide, carbon monoxide or carbon dioxide, according to The Fresno Bee as cited by the Irish Mirror.

The Daily Express US, citing The Fresno Bee, listed the eliminated factors as suicide, being caused by a gun or other weapon, alcohol, illegal drugs, lightning strike and exposure to cyanide, carbon monoxide or carbon dioxide.

One theory under consideration was that toxic algae found in nearby water had poisoned the family, according to the Irish Mirror.

Investigators worked with toxicology experts to determine whether the algae could have poisoned the family, according to the Irish Mirror.

Sheriff Briese confirmed there was "no evidence they drank any of that water," according to LancsLive.

The area around the trail was also known to contain mines, according to the Irish Mirror.

Sheriff Briese said one mine was located close to where the family were found but that there was no evidence the family had come into contact with it, according to the Irish Mirror.

Why this case matters for remote hikers

The case highlights risks of long hikes in remote, high-temperature terrain without water or shelter and shows how phone-data extraction can reconstruct final movements and inform search decisions, according to Particle.

The eight-mile route left the group exposed to 42°C heat with a single empty water bladder backpack, snacks and baby formula documented at the scene, according to LancsLive and the Irish Mirror.

The absence of mobile reception meant calls and texts could not transmit, although later extraction still revealed attempted calls, unsent pleas for help and time-stamped images from 7.45am to around 12pm, according to the Irish Mirror.

The two-day interval between the babysitter finding an empty house and the discovery on August 18, 2022 underscored how a missed check-in led relatives to report the family missing and directed search teams to first locate the car, according to the Irish Mirror.

For prepared adventurers, the documented sequence — a morning start, a midday creek photo, failed communications, and bodies found after most of the hike was completed — provides a concrete example of how quickly water depletion and lack of shelter can become fatal on remote trails, according to Particle and the Irish Mirror.

Sources referenced