Family found dead in Sierra Nevada died of heat exposure

(CN) — A family of three all died from extreme heat exposure, or hyperthermia, on a trail in Mariposa County in the Sierra National Forest, law enforcement said during a Thursday press conference. 

John Gerrish, Ellen Chung, their 1-year-old daughter Miju Chung-Gerrish and their family dog were all found dead in proximity to Devil’s Gulch near the South Fork of the Merced River in Mariposa County on Aug. 17. 

“Essentially, it’s heatstroke,” said Jeremy Briese, Mariposa County Sheriff during Thursday’s press conference. “Heat-related deaths are extremely difficult to investigate.”

Speculation was that the family died of exposure to toxic algae or may have drank from the Merced River and ingested anatoxin-a, but Briese said the toxicology reports from the county coroner found no evidence for either hypothesis. Law enforcement was quick to rule out foul play during the early stages of the investigation. 

But questions remain, as the sheriff acknowledged it was strange for all four members of the family to expire simultaneously in the same area of the trail. 

“The family was all found in the same area of the trail,” he said. 

Investigators found that Gerrish and Chung were well-practiced hikers, but may have underestimated the combination of high temperatures and steep terrain coupled with a lack of shade and water. 

The couple left with their daughter and dog on the morning of Sunday, Aug. 15. They drove to the Hite Cove Trail, which is about 15 miles due west to the westside entrance of Yosemite National Park. 

They walked about 2 miles on the Hite Cove Trail near the river, before taking the Savage Lundy Trail, which ascends aggressively from the steep river canyon to the ridges above. 

“There is a steep incline on the trail, which is south to southeast facing and exposed to constant sunlight,” Briese said, adding that the Ferguson Fire in 2018 reduced the trees and the shade. 

The temperatures soared as the day proceeded, with a high of 107 degrees at one point. When the family of three and their dog were found on the morning of Tuesday, Aug. 17, they had one 85-ounce water bladder located in a backpack and no other water receptacles. The water bladder was essentially empty except for a trace amount the sheriff’s office was able to test. 

There was no anatoxin-a found in the water. 

Samples were taken from the Merced River and anatoxin-a was found, but law enforcement does not currently believe ingestion of water played a role in the mysterious deaths. 

Briese said the FBI continues to hold Gerrish’s cellphone and investigators hope to get more clarity about the last moments of the family. 

The Gerrish and Chung families released a statement at the press conference, praising the sheriff’s office for its work and thanking the community for galvanizing behind their family. 

“The lack of knowledge and certainty as to the reasons for their death — the why, where and the how fill your mind all the days and all of the nights,” the family said. 

But they expressed appreciation for the sheriff’s constant communication. 

“The loss of a close relative is a pain beyond words,’ the family said, saying that the loss of a one-year-old baby is “indescribable.”

The family wasn’t found until Tuesday after the family babysitter showed up to work on Monday morning, Aug. 16, only to find the house empty. She gradually began to grow increasingly worried and finally contacted the family Monday afternoon, who contacted the sheriff’s office later that night. 

The family was found on Tuesday morning, having completed 6.4 miles of an 8-mile loop. 

“Be prepared,” Briese said when asking what people could do to safely hike in the area. The forest service has closed the trail to hikers, but Briese deferred questions to them and did not think toxic algae or other environmental toxins played a role. 

There is a mine shaft within a couple of miles of where the family was found, but Briese said there is no evidence they entered the shaft or even went near it. 

Gerrish used a phone app to plot his route through the national forest near Yosemite so investigators are hopeful a careful analysis of the phone could reveal what went wrong. 

Heat stroke-related deaths are relatively common in California, particularly in places like Death Valley National Park, but given the different reactions of different people to heat stresses, it is wildly coincidental that both Gerrish and Chung would die of hyperthermia at the same time in proximity to one another. 

But Sheriff Briese said it's the most plausible explanation given the present evidence. 

“We’re confident in our findings and our investigation supports the findings from the coroner’s office,” he said. 

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