Heat and Dehydration Likely Cause of Mysterious Hiking Deaths in California This Summer

Heat and Dehydration Likely Cause of Mysterious Hiking Deaths in California This Summer
A vehicle entering the Sierra National Forest northeast of Fresno in the foothills of the Sierra Nevada mountains on Sept. 11, 2020, during a forest fire in the area. (Photo: Frederic J. Brown, Getty Images)

Mariposa County Sheriff’s officials believe they now know what likely led to the mysterious deaths of a California family of three and their dog while hiking earlier this summer: heat and dehydration. The determination came after months of concern that other possible causes, including toxic algae, may have posed a continued threat to hikers in the area.

In mid-August, the bodies of married couple John Gerrish and Ellen Chung, their 1-year-old daughter, Miju, and their dog were discovered along a hiking trail in the Sierra National Forest of Northern California, following a friend’s missing person report. They were located some distance away from their car and had no visible signs of trauma or other indications of what killed them.

Officials were careful to note from the start that they had no single theory as the family’s cause of death. But one possible culprit was exposure to toxins produced by certain species of blue-green algae from a nearby water source, a known danger in the area. In early September, tests did find high levels of a particular toxin in a river close to where the family was found, though officials again urged that this did not necessarily mean it was responsible for their deaths.

Finally, at a news conference this Thursday, Jeremy Briese, Mariposa County sheriff and coroner, announced the conclusion of their investigation, which included autopsies of the family and toxicology tests. Near as they can tell, the most likely cause of death was exposure to extreme heat, known as hyperthermia, and probable dehydration as a result. Though the dog’s death wasn’t specifically determined, they do believe heat likely killed it as well.

“This is an unfortunate and tragic event due to the weather,” Briese said, according to The Fresno Bee.

Briese noted that the trail they were found on, the Savage Lundy Trail, could be an arduous journey even for experienced hikers, as both parents were. Around their suspected time of death on August 15, the temperature in the area had climbed to over 100 degrees Fahrenheit (38 degrees Celsius), he added. Worse still, the part of the trial they were on had little shade, due to an earlier forest fire. Federal data show this was California’s hottest summer on record, a symptom of the climate crisis. (So, too, are wildfires.) The group had apparently also only brought along one water container to share.

As for the algae, despite its nearby presence, officials found no evidence that the family had been exposed to it, including by drinking contaminated river water. Notably, while toxic blooms can be deadly to wildlife and pets, no human deaths have been linked to the specific toxin found in the national forest, known as anatoxin-a, Briese said. Parts of the trail are still scheduled to remain closed to the public through the end of the month.

There are specifics left unknown about the family’s final moments, near the end of the trail and less than two miles away from their vehicle. Officials said they’re working with the FBI to look at Gerrish’s phone data in hopes of finding more clues. But for now, the investigation has largely come to a close. Survivors of the family, for their part, thanked the officials for their work.

“They felt our pain, shared the distress of our loss, and responded with sympathy, empathy, and total dedication trying to find some answers for us,” the family said in a statement shared at the news conference.