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Sheriff reveals what killed California family of hikers

A family died in the Sierra National Forest while hiking in August. Authorities announced on Thursday (Oct. 21) that they died from hyperthermia and possible dehyrdation.
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A family of hikers who mysteriously died two months ago along a hiking trail in California died from hyperthermia and probable dehydration, the Mariposa County Sheriff revealed during a press conference on Thursday (Oct. 21).

The bodies of John Gerrish, Ellen Chung, their 1-year-old daughter Miju and their 8-year-old dog Oski were found on Aug. 17 along the Savage Lundy Trail near the Merced River in the Sierra National Forest, Live Science previously reported. There were no signs of trauma to their bodies, and investigators couldn't immediately find a cause of death.

"Heat-related deaths are extremely difficult to investigate," Mariposa County Sheriff Jeremy Briese said at the press conference. Since the bodies were found, the Mariposa County Sheriff's department has worked with the FBI, toxicologists, and environmental and other experts to determine what caused the tragic deaths. The investigators looked into various possibilities, including whether high levels of toxic algae in the Merced River or fumes from nearby abandoned mines could have poisoned the family.

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No evidence suggests that the family members ingested any of the contaminated water or that they accessed the nearby mines, Briese said. The investigators also recently ruled out other causes of death, such as a lightning strike, gun wounds or suicide. 

The autopsy report, the timeline of their disappearance, the weather of that weekend, the trail that they took, the lack of shade along the trail and their lack of water all pointed to hyperthermia and probably dehydration as the cause of death, Briese said. "We're confident of our findings."

Hyperthermia occurs when extreme outside temperatures cause the body's temperature regulating mechanisms to break down, according to The National Institutes of Health. When the body's temperature shoots up to above 105 degrees Fahrenheit (41 degrees Celsius), it can damage the brain and other organs, cause muscle cramps, fatigue, weakness, dizziness and ultimately can cause death, Briese said. 

The dog Oski's cause of death "remains undetermined," but evidence suggests he was also suffering from heat-related issues, he said.

The bodies were discovered about 1.6 miles (2.6 kilometers) from their car at the head of an 8-mile (12.8 km) loop that includes the Hite Cove trail and the Savage Lundy trail. Investigators discovered an empty, 85-ounce (2.5 liters) water bladder, but no other water container or water filtration system. They also found some snacks and a little bit of baby formula. It's not clear if they all died around the same time or not.

The trail they took had steep inclines and no shade on parts of it; and temperatures there that day reached up to 109 F (43 C). "My message would be to prepare if you're going to hike," he said. This was an "unfortunate and tragic event due to the weather."

Originally published on Live Science.

Yasemin Saplakoglu

Yasemin is a staff writer at Live Science, covering health, neuroscience and biology. Her work has appeared in Scientific American, Science and the San Jose Mercury News. She has a bachelor's degree in biomedical engineering from the University of Connecticut and a graduate certificate in science communication from the University of California, Santa Cruz.