A couple, their baby and their dog died on a California hiking trail - and officials don’t know why

The Mariposa, Calif., home of John Gerrish and Ellen Chung was quiet on Aug. 16 when their 1-year-old daughter’s nanny arrived. The family - including the dog, Oski - was nowhere to be found. Their truck was missing, too. As the hours wore on without a word from Gerrish or Chung, who had set out for a hike the day before, a sense of panic began to set in.

The couple’s house sits near the head of Hites Cove Trail, and hours after the family was reported missing at about 11 p.m., the trailhead is where police started looking. A sheriff’s deputy found the couple’s truck parked near the trail’s entrance around 2 a.m., the San Francisco Chronicle reported.

Nine hours later and 1.5 miles from the family’s truck, in an area known as Devil’s Gulch, a search-and-rescue team found Gerrish, Chung, their daughter, Miju, and the dog.

They were all dead.

Gerrish was in a seated position with the baby and dog beside him, according to the Chronicle. Chung was a little farther up the hill.

Authorities still don’t know how it happened. An autopsy recently completed on the bodies yielded no conclusive results about the cause of the deaths, CNN reported. A toxicology report, which could take several weeks, is pending.

A necropsy is being performed on Oski, the dog, but the Mariposa County Sheriff’s Office said no other animals were found dead in the immediate area.

“It’s just so tragic and mysterious,” a close family friend, Steven Jeffe, told The Washington Post on Sunday evening.

Gerrish and Chung moved to Mariposa from San Francisco in March 2020, Jeffe said. The pandemic made the slow life look increasingly attractive for the young professionals. Gerrish worked at Snapchat, and Chung was working toward a master’s degree in family therapy, he said.

When they lived in San Francisco, the couple enjoyed DJing and going to clubs, Jeffe said. But since moving out to Mariposa - about a three-hour drive east of the city and a 40-mile drive to Yosemite - they became “avid outdoor people.”

When police found their bodies, there were no signs of trauma, the Fresno Bee reported. There was no suicide note or indication that the deaths were intentional, according to CNN. Although temperatures reached as high as 109 degrees the day the family hiked, dehydration was deemed unlikely because there was still water in the family’s hydration pack, the Chronicle reported.

Snakebites have not been ruled out, although that cause is unlikely because there was no physical evidence of wounds, the sheriff’s office told CNN.

The lack of definitive answers has led investigators to imagine other, more unusual causes. Carbon monoxide poisoning from a mine or toxic algae in the nearby Merced River are among the leading theories.

“At this point, we can’t rule out anything,” Mariposa County sheriff’s deputy Kristie Mitchell said, according to the Fresno Bee.

About a month before the family was found dead, the U.S. Forest Service warned that “a high concentration of algae bloom” had been found in the Merced River near Hites Cove, where Gerrish and Chung were hiking. The Forest Service warned visitors not to swim or let their pets “enjoy” the water.

But reported human deaths from freshwater algal blooms are rare, the Chronicle reported. David Caron, a biological sciences professor at the University of Southern California, told the newspaper that although freshwater bacteria are a threat to people and animals, it would take high concentrations to kill humans rapidly.

“It’s conceivable that it is the cause,” Caron said. “But a lot needs to be done forensically to tie it to toxins.”

Poisoning from mines is also a possibility. When the family was found Tuesday, first responders treated the scene as a hazmat site because carbon monoxide may have leaked out from nearby mines. But the hazmat declaration was lifted Wednesday, and the cause is looking less likely, Mariposa County Sheriff Jeremy Briese told the Fresno Bee. The closest mine Briese told the paper he knew of was three miles from where the family was found.

“We have not found any old mine shafts near the area,” he added. “There are some mine shafts, but we can’t confirm if that’s the cause yet.”

Meanwhile, Jeffe and Mariposa residents remain frustrated by the lack of answers.

“We’re just devastated by the loss,” Jeffe told The Post. “But I think the community is more like, ‘What the heck happened?’ It’s just so crazy.”