Investigators Reveal What Killed Family Found Dead After Sierra Forest Hike

More than two months after a family and their dog was found dead on a hiking trail in the Sierra National Forest, investigators have released the cause of their deaths.

The bodies of John Gerrish, Ellen Chung, their daughter Aurelia "Miju" Chung-Gerrish, 1, and the family's dog Oski were discovered, together, on the morning of Tuesday, Aug. 17. They had left on for a hike on Sunday, Aug. 15 along the three-mile long Savage-Lundy Trail in the forest, in an area known as Devil's Gulch near the community of Hites Cove; it was along the trail that their bodies were discovered.

Their babysitter arrived on Monday morning to their empty house and, after a day without reaching them, friends reported them missing on Monday night.

There were no signs of foul play, and investigators initially classified the area as a hazmat investigation, concerned that either toxic algae blooms in streams near the trail or gases from nearby mines might have been the cause of their deaths.

On Thursday, the Maricopa County Sheriff's Office announced that, after autopsies and toxicology tests, the mystery of the family's near-simultaneous deaths had been solved.

"The cause of death for Jonathan Gerrish, Ellen Chung and Aurelia 'Miju' Chung-Gerrish has been determined to be hyperthermia, and probable dehydration due to environmental exposure," the department said in a statement.

Though Oksi's cause of death has yet to be officially determined, investigators say the dog appeared to have had heat-related issues as well.

"Heat related deaths are extremely difficult to investigate," Sheriff Jeremy Briese said at a press conference, "and I want to thank you all for being patient with us as we investigated this case."

Investigators say they were able to determine that Gerrish had decided on the route for their eight-mile hike on Saturday night, using an app on his phone to plot it out — but the app did not calculate either the trail mileage or the elevation changes. The route he had plotted would have taken the family in a loop that ended back at their car. (His cell phone is "still being looked at" by the FBI, according to Briese, though they have yet to be able to access its contents. He indicated in response to questions that they'd gotten information about the app usage from the company directly.)

The family began their hike along the trail between 7:45 a.m. and 8:00 a.m. that morning, according to a witness that was hiking along the road and saw them drive up and later observed their car parked. According to investigators, the family had only one, 85-oz. camelback water bladder and a bottle full of formula for the three people and the dog. When they left the Hites Cove trail head — which sits at an elevation of 3,880 ft. above sea level — it was about 75 degrees Farenheit. The couple had their young daughter in a backpack-style carrier.

They walked about 2.2 miles downhill from the trailhead, descending 1,950 feet to an elevation of 1,930 ft. above sea level before arriving at the intersection of the Hites Cove trail and a U.S. Forest Service trail. The temperature when they likely would've reached that point in their hike had risen approximately 20 degrees, to between 93 and 99 degrees Fahrenheit.

The family continued another 1.9 miles to the Savage Lundy Trail intersection, dropping only about 100 feet in elevation. Investigators believe that, at the hour they would've arrived there, it would have been between 99 and 103 degrees on the trail.

Investigators aren't sure at exactly what point in the day the family started up that section of the Savage Lundy trail, which is a steep incline with switchbacks. The trail also lacks any shade since the Ferguson fire of 2018, and its south-southeast facing slope is in the sun all day. But, between 12:50 p.m. and 2:50 p.m., the temperatures on the trail were between 107 and 109 degrees, and it did not begin to cool off until around 4:50 p.m. that day.

The family completed around two miles of the uphill Savage Lundy trail, climbing another 2,000 feet — less than half a mile of elevation from the trailhead, and close to the original elevation at which they started.

That is where their bodies were found by investigators on Tuesday morning. The family was approximate 1.6 miles from the end of their looped trail and their car; Gerrish's phone reportedly had no service in that location. The 85 oz. water bladder in their backpack was empty, and investigators found no other water bottles or water filtration systems with their bodies, and no evidence that the family had ingested water from the Merced River, which paralleled the second trail section they utilized.

Investigators did, however, still test six samples of the water along the trail and found a toxin from the algae blooms — Anatoxin A — in it, but that toxin is not known to be deadly to humans. The one mine in the area was nearly two miles from where the family's bodies were found, and there was no evidence that the family had come anywhere near it.

The Gerrish/Chung family provided the Mariposa County Sheriff with a statement.

"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," it said.

"Our hearts will never forget the beautiful lives of Jonathan, Ellen, Miju and of course Oski," the added. "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 soughing through the branches we will hear them and we will remember."