The couple had backpacked in the Himalayas, ridden camels through the Gobi Desert and checked off Burning Man, even creating their own hashtag, an amalgamation of their first names: #jellonadventures.
So a day of hiking in the Sierra National Forest, even with the demanding switchbacks and triple-digit heat, would not have been unusual for Jonathan Gerrish and Ellen Chung, husband-and-wife transplants from San Francisco who had recently become parents to a little girl, Miju, during the coronavirus pandemic.
But the trek would be the family’s last: Search teams found all three of their bodies on Aug. 17, one day after the family was reported missing not far from Yosemite National Park. The family’s dog, Oski, an Aussie-Akita mix, was also found dead.
More than two weeks later, investigators are still confounded by what caused their deaths. Teams in hazmat suits had already combed the area for clues. On Saturday, the U.S. Forest Service closed trails and recreation sites near where the bodies were found.
The Forest Service had previously posted warning signs about potentially toxic algae blooms in the area. The agency said it had taken the step to “protect the public from unknown hazards.”
That development further disconcerted those who knew the family, including Steven Jeffe, a friend and neighbor in Mariposa, Calif.
“It’s mysterious,” Mr. Jeffe said in an interview on Wednesday, “the unknown of what danger possibly lies there.”
Mr. Jeffe said he became friends with the couple when all of them lived in San Francisco. He described Mr. Gerrish, a software engineer born in Britain, and Ms. Chung, a graduate student in family therapy who had worked as a yoga instructor, as outdoor types who were experienced hikers.
Mr. Gerrish, 45, had worked as a software engineer for Google, according to his LinkedIn profile. Most recently, he had worked for Snapchat, according to Mr. Jeffe. Ms. Chung, 30, was raised in Southern California, Mr. Jeffe said.
“It’s such a beautiful family,” Mr. Jeffe said. “It’s obviously so devastating.”
Initial autopsy results have provided no answers to the authorities. Investigators said that there were no signs of trauma and that they were investigating possible lightning strikes in the area.
A spokeswoman for the Mariposa County Sheriff’s Office said in an email on Wednesday that there were no new updates in the investigation.
In an interview with The Fresno Bee, Sheriff Jeremy Briese said that he had never encountered such a mysterious case.
“It’s frustrating, and we’re not going to rest,” Sheriff Briese said. “Our biggest mission is safety, but also the family and bringing closure, and being able to support them through this tragic time.”
On Aug. 19, the California State Water Resources Control Board, using a water quality reporting map on its website, warned the public to “stay away from algae and scum in the water” near the south fork of the Merced River in the Sierra National Forest.
An incident description said that the agency had received a report of a “suspected illness” in the area. The warning previously made reference to a fatality, but was changed to say illness, The Bee reported.
“Do NOT let pets go in the water, drink the water, or eat scum on the shore,” the warning said. “Keep children away from algae. Do not eat shellfish from this waterbody.”
The Forest Service, which temporarily closed all national forests in California this week because of the wildfires spreading across the state, did not respond to a request for comment.
According to the Sheriff’s Office, the family was reported missing at 11 p.m. on Aug. 16. The next day, search teams found the couple’s vehicle near one of the gates to the Sierra National Forest. Their bodies were found a short time later near Devil Gulch.
“My thought initially was perhaps the car veered off the trail,” said Mr. Jeffe, who cut short a trip to Croatia when he learned that the bodies had been found. “People were going to go out and look.”
In an Instagram post in August 2020, Ms. Chung beamed over the birth of her daughter.
“Their daughter was everything,” Mr. Jeffe said. “They were very devoted parents.”