Ellen Chung, Jonathan Gerrish, their 1-year-old daughter Miju, and the family dog Oski, all died on the Savage Lundy Trail, a hiking trail in the Sierra National Forest, in northern California. They succumbed to hyperthermia and probable dehydration during a “deadly trifecta” of heat, elevation, challenging terrain, authorities have concluded. 

Just before 9:30 a.m., Aug. 18, the two parents, baby and pet were found “deceased near the Devil’s Gulch area in the Southfork of the Merced river drainage” in the words of the Mariposa County Sheriff’s Office Facebook posting.

It wasn’t clear at first what happened. The Devil’s Gulch area is an abandoned gold mine, and the first responders thought this might be a death of carbon monoxide. A hazmat team was called. Authorities explained that in the old mines wooden timbers rot, allowing CO buildups. But there was no CO poisoning. 

Another theory, developed early in the investigation, said Ellen Chung, Jonathan Gerrish and their baby may have died of toxic algae. High levels of toxic algae had been detected in the Merced River. But there is no evidence any member of the family ingested any of it.

At the center of the heart-breaking story is the lack of water: Ellen Chung and Jonathan Gerrish didn’t bring enough with them. As a consequence, they died in an unsuccessful effort to save the life of their baby.

The U.S. Forest Service advises that hikers bring 160 ounces of water for each adult in the party, and 16 ounces for each infant or dog.   

Ellen Chung, Jonathan Gerrish, Miju and Oski were found dead two days after they took off in their trek, on which they had taken only 85 ounces of water. 

The San Francisco Chronicle obtained eight pages of investigative reports, and provided their substance in a story Friday.

Ellen Chung was a yoga instructor and graduate student. Jonathan Gerrish was a Snapchat engineer. A pandemic-inspiured move out of San Francisco had brought them to Mariposa.

Chung and Gerrish were last seen on Aug. 15. The temperature in the Sierra National Forest that day was 99 degrees at midmorning. It peaked in the afternoon at 109 degrees. Their dog, Oski, an Aussie-Akita mix, had a thick coat which would have made it especially susceptible to heat.

Gerrish had a cellphone with him on the hike. It was found in the front pocket of his shorts after his death. But cellphone coverage along the trail is spotty.

Investigators haven’t been able to access that phone (Google Pixel 4) to check whether he had tried to make calls or send texts in his final hours.

The documentation reviewed by the Chronicle included an email that a survival trainer sent to detectives. It spelled out the likely course of events in the final hours of this family in this way:

“Sadly, I believe they were caught off guard, and once they realized their situation, they died trying to save their child and each other. It is likely the child began to succumb first, which hurried the parents’ efforts up the hill. When one could no longer continue, they stayed behind to care for the child and pet, while the other [Chung] tried to forge on and get help for their loved ones. It is a tragedy of the highest order.” Chung’s body was found roughly 13 feet in elevation higher than the rest of the family.

The couple had no water filtration system with them.

In a statement, family members thanked the sheriff’s office for its work, and added, “Some questions have been answered, and we will use this to help us come to terms with this. They will remain with us wherever we go, or whatever we do. In the future when we sit beneath the trees, hearing the wind soar beneath the branches, we will think of them and we will remember.”