Family's tragic final text before dying in national park: 'Help us'

A family who tragically died while hiking in northern California last year had desperately tried getting help as authorities reveal their final text message.

But due to having no reception, the plea for help didn't go through.

Jonathan Gerrish, 45, and his wife Ellen Chung, 31, were found dead on a remote hiking trail near Yosemite National Park, along with their one-year-old daughter Miju and their family dog Oski, and investigators have since been piecing together their final movements.

Phone records released by the Mariposa County Sheriff’s Office showed Mr Gerrish had tried texting someone shortly before midday on August 15 expressing their desperate need for help.

"Can you help us. On savage lundy trail heading back to Hites cove trail. No water or ver (over) heating with baby," it said.

Authorities first believed lightning strikes or poisoning from algae-tainted water, among other suggestions, was the cause of death, it was previously reported, but after further investigation, this was ruled out.

The new findings confirm the cause of death was in fact hyperthermia — extreme heat stroke — and probable dehydration due to environmental exposure, a statement from authorities revealed.

Final cry for help

Despite their cry for help, the text never went through, investigators said, and records also reveal a number of attempted calls made by Mr Gerrish which also failed. However, there was no call to 911.

Phone records also show a series of selfies and family photos taken on the hike, including a screenshot of their location from a trail app they'd used in the hope someone could locate them.

The temperature on August 15 reached 43 degrees Celsius in the steep mountain terrain and the family had run out of water, ABC reports. An empty 2.5-litre bottle was found with their bodies.

They'd reportedly hiked 10.2 kilometres with the baby strapped to them and were just 2.5 kilometres away from their car.

The bodies of the family were found two days later after relatives had reported them missing. Their deaths baffled investigators who've spent months tracking the family's final movements.

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Family friend Sidney Radanovich last year described the couple as avid hikers who were particularly fond of exploring the area, Huffington Post reports, and described them as "such a loving couple".

Sheriff Jeremy Briese said the phone data were "the last thing both the family and detectives were waiting on," and the information "confirms our initial findings". The case is officially closed.

"I am very proud of my team and our partner agencies for all the work they put in," he said.

"Their dedication has allowed us to close this case and answer lingering questions the family had, bringing them a little peace."

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