"Heat-related deaths are extremely difficult to investigate, and we want to thank you all for being patient with us," Briese said during a press conference.
The sheriff's office investigation, involving over 30 local, state and federal agencies, found that the family hiked along miles of trails in the days leading up to their deaths.
A witness saw the family on the Hites Cove trail on August 15, where they embarked on a 2.2-mile walk to a U.S. Forest Service trail parallel to the south fork of the Merced River with an elevation of 1,930 feet. From there, they walked 1.9 miles to the Savage Lundy Trail, then ended up on a steep incline where temperatures reached 107 to 109 degrees due to a lack of shade and high elevations; the sheriff said temperatures when the family began their hike was in the mid-70s. At 105 degrees, hyperthermia can cause brain and organ damage. This can lead to a fatal heat stroke.
When their bodies were found August 17, the only water supply with them was an 85-ounce water bladder. No additional water containers or filtration systems were found.
Briese did not confirm the cause of death for the family's eight-year-old dog Oski.
During the conference, Briese played drone footage showing the trails that the family walked in the days before their bodies were found. Briese also noted that there is no evidence that they ingested any water that tested positive for toxic algae. Six separate laboratories conducted water samples; testing that was done on the water taken from several locations along the Merced River was positive for algal blooms.
The sheriff's announcement caps a nearly three-month investigation into the deaths of the young family.
The family was found dead Aug. 17 in the Devil's Gulch area in the south fork of the Merced River in the Sierra National Forest, the Mariposa County Sheriff's Office said. Responding agencies initially treated the scene as a hazmat situation because of uncertainty about the cause of the fatalities.
Over the course of the investigation, autopsy data ruled out a wide variety of factors, some of which were the subject of much media speculation. This included lightning strikes, carbon monoxide or dioxide poisoning, exposure to cyanide, illegal drug or alcohol consumption and acute or blunt-force trauma.
And as the investigation continued, areas by were the family had hiked were all subject to closures.aside">
The Merced River Recreation Site was shut down by officials in late August "due to unknown hazards found in and near the Savage Lundy Trail." The Bureau of Land Management also closed campgrounds and recreation areas along the Merced River upon discovery of toxic algae blooms in the water.
Cell phone data has yet to be revealed; it is still under FBI investigation.
The family relocated to the Northern California town of Mariposa from San Francisco during the COVID-19 pandemic when Gerrish was presented an opportunity to work remotely for good, the Sacramento Bee reported in August.
The Bee reported Gerrish was a software engineer at Snapchat, while Chung was in graduate school to become a family and marriage therapist.
Before relocating to the small town, both were avid concert and festivalgoers; social media posts dating back to 2017 show Chung and Gerrish at shows with large groups of friends.
The two wanted to raise Miju in a "quiet, slow-paced environment" surrounded by nature, in a setting unlike the hustle and bustle of San Francisco.
In recent months, multiple hikers, including ultramarathon runner Philip Kreycik and athlete Fred Zalokar, were found dead in California after embarking on long, precarious treks.
"Prepare if you're going to hike ... the community is resilient, the community is safe, this is again unfortunate and tragic," Briese said.
This is a breaking story and will be updated.
SFGATE California parks editor Ashley Harrell contributed to this report.
Source : https://www.sfgate.com/bayarea/article/Cause-death-reveal-California-family-hike-Yosemite-16552512.php1990