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Investigators Determine Cause of Death for Family Who Died on California Hiking Trail

Parents and 1-year-old died of heat exposure and possible dehydration, sheriff says.

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A family of three and their dog found dead on a California hiking trail in August passed away from heat exposure and possible dehydration, the Mariposa County Sheriff’s Office announced on Thursday.

In a press release, the sheriff wrote that Jonathan Gerrish, Ellen Chung, and their 1-year-old daughter Miju passed away from “hyperthermia and probable dehydration due to environmental exposure.” While investigators did not determine a cause of death for Oski, the family’s 8-year-old Aussie/Akita mix, the sheriff’s office said it believed the dog had also overheated.

The announcement provides some resolution to a case that had vexed investigators and the hiking public, leading to trail closures as officials worked to determine if some unidentified danger in the area had killed the Gerrish-Chung family. After the family’s babysitter was unable to locate them on August 15, the sheriff’s office began looking for them, eventually calling in search and rescue teams after finding the family’s truck at the Hites Cove Trailhead near Mariposa, California. Hours later, searchers located the family’s remains 1.6 miles away from their vehicle on the Savage Lundy Trail.

Investigators quickly ruled out trauma, initially treating the site where the family was found as a hazmat site. As the investigation continued, they were able to confirm the family hadn’t died from a list of other causes, including toxic gases from abandoned mines, carbon monoxide poisoning, drugs, or suicide. One persistent theory was that the family had died after drinking water from the nearby Merced River which was contaminated with toxic algae. That possibility led the Forest Service to close roads, campgrounds, and trails in the South Fork Merced area of Sierra National Forest in September. In an announcement, the Forest Service said the closure was to “provide for public safety due to unknown hazards in and near the Savage Lundy Trail.”

State water officials later tested nearby water sources, with the help of six separate laboratories; in its press release, the sheriff’s office said interested parties could contact the state water board for the results. However, the agency noted that there was no evidence that the family had drank water from the river, and that regardless, there have been no documented human deaths from Anatoxin A, the toxin initially suspected.

Instead, officials say, the family seems to have died from overheating while hiking on the occasionally steep, exposed Savage Lundy Trail. The 2018 Ferguson Fire killed many of the trees in the area, leaving the path exposed to the sun. The temperature on the day that the Gerrish-Chung family embarked on their hike rose to a punishing 109 degrees, and investigators say the family had only one water container, an 85-ounce bladder, with them, which searchers discovered empty.

In an email, Backpacker columnist and associate professor of emergency medicine at Columbia University Christopher Tedeschi wrote that two months isn’t an unusual amount of time for authorities to take to determine a cause of death. While there are some signs of heat stroke that a pathologist might be able to detect after death, overall, he says, “there aren’t really too many physical clues to indicate heat illness after the fact.”

“I think it’s definitely tricky to recognize this post-mortem,” he writes.

The family joins a handful of hikers who died of heat-related causes over the summer, which saw popular destinations across the western United States hit record high temperatures. Visitors died in Death Valley and the Grand Canyon, and Phoenix, Arizona put restrictions on its local trails after a surge in rescue calls from heat-stricken hikers. Climate researchers warn such anomalous heat waves may become more common as the earth continues to warm, leading to additional deaths.

In a statement, the family’s relatives thanked the Mariposa County Sheriff’s Office and said that “the loss of a close relative is a pain almost beyond words. When that loss is multiplied by four and one of that four is a baby of just one years old, then the pain is indescribable.”

“Some questions have been answered and we will use the information as a way of helping us come to terms with the situation, however the question “why” can never be answered and will remain with us,” they said. “Our hearts will never forget the beautiful lives of Jonathan, Ellen, Miju and of course Oski. They will remain with us wherever we go and whatever we do. In the future, when we sit beneath the trees listening to the wind [sighing] through the branches we will hear them and we will remember.”