New details are emerging about the events surrounding the deaths of a California family on a hiking trail in a new report from The San Francisco Chronicle.
Ellen Chung, 31, Jonathan Gerrish, 45, their daughter Miju, 1, and their 8-year-old dog Oski were found dead along a hiking trail in the Sierra National Forest on Aug. 17, PEOPLE previously reported.
In October, the Mariposa County Sheriff's Office announced that the family had died from hyperthermia and probable dehydration.
According to records released to The Chronicle under California public records laws, investigators say, "All the evidence kept pointing back to heat exposure and lack of water."
A woman walking her dogs had spotted the family's gray Ford F-150 Raptor parked at the trailhead, which was located just a few miles from their home, at about 7:45 a.m. local time on Aug. 15, the alleged day of the hike.
The temperature was 76 degrees early in the day but peaked at 109. Investigators said ground temperatures likely would have been higher due to the lack of shade from trees that were burned during the 2018 Ferguson Fire, per The Chronicle.
The family was first reported missing on Aug. 16 after their babysitter found the home empty, as PEOPLE previously reported. The Chronicle reports that the babysitter was the last person to see the family alive on the afternoon of Aug. 13 after cleaning their house.
The unidentified woman's final communication with Chung came later that evening, per the report, when she received a text from the mother featuring a video of Miju starting to walk.
Rosanna Heaslett John Gerrish, Ellen Chung and daughter Muji
After arriving at the residence around 11 a.m., the babysitter reportedly discovered the couple's wallets, most of their cell phones, and a diaper bag that they typically kept with them.
The woman then called the building's construction manager, who joined her in sending out calls and texts, per The Chronicle. A deputy wrote that the construction manager was not initially worried by the babysitter's report as he considered Chung and Gerrish to be a "very active family."
The two reportedly drove around the area in search of the couple at 5 p.m., but with no luck. At 11 p.m. — 12 hours after the babysitter came upon the empty house — the pair called the sheriff, and a search was initiated.
The family's car was found at the trailhead on the morning of Aug. 17. The Chronicle reports that the bodies of Gerrish, Miju, and Oski were located roughly 1.6 miles below "on a series of steep switchbacks of the Savage Lundy Trail."
Chung was found about an hour later at 10:30 a.m. after a deputy noticed "some disturbed dirt on the uphill side of the trail that appeared that something or someone had tried to go up the hill," per the report. The woman was found about 13 ft. higher than her family.
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Investigators found various items in Chung's backpack such as a snakebite kit, a knife, bug spray, first aid kit, extra diapers, two empty sippy cups — one of which appeared to have the remnants of formula inside — and a teething wafer wrapper, The Chronicle reports.
The woman also had a 2.5-liter Osprey Hydraulics LT water bladder in her possession, which detectives said had only a "few remaining drops" of water left inside. No toxins were found in the water. A Ford key fob was also found about 100 ft. below where Gerrish was found.
Rescuers did not find evidence of foul play, per the report.
Investigators are still attempting to access a Google Pixel 4 cell phone found in the front pocket of Gerrish's shorts. Phones obtained by deputies through a search warrant on the couple's home on Aug. 17 had missed messages from the days prior.
One U.S. Forest Service volunteer told a deputy the family appeared "completely unaware of the dangers" they faced, according to The Chronicle. That individual is said to have hiked the trail more than a dozen times.
Another volunteer said he would often wait at the bottom of the trail until sunset in order to finish the hike in the shade. A Forest Service employee familiar with the trail also told investigators that locals typically "stay clear" of it in the summer, per the report.
One expert interviewed by detectives suggested the family had overheated, which caused their brains and organs to shut down. A Modesto doctor who works with extreme heat victims told investigators that individuals can die within a couple of hours of having a heatstroke.
Additionally, the family's dog — an Aussie-Akita mix — was not bred for such warm conditions. Both breeds typically sport thick fur coats.
In October, Sheriff Briese told reporters, "This is the first hyperthermia cause of death that I've witnessed here in 20 years."
Gerrish and Chung's relatives said in a statement via the Mariposa Public Information Office that the "pain" they feel from their loved ones' deaths "is indescribable."
The couple's family noted that "the lack of knowledge and certainty as reasons for the death" led them to initially question the circumstances surrounding the situation.
"Our hearts will never forget the beautiful lives of John, Ellen, Miju and of course, Oski," the statement concluded. "They will remain with us wherever we are and whatever we do."