Investigators are still trying to determine what caused an SUV carrying a family of eight to plunge off a California cliff. Five members of the Hart family - a free-spirited brood from Washington state who grew their own food and took up activist causes - were found dead.

Searchers kept looking Friday for three more children believed to have been in the vehicle when it went over a scenic coastal overlook and landed on rocks in the Pacific Ocean below. The missing children may have been washed out to sea.

Some family friends describe the Harts as tight-knit and loving, but neighbors said they saw signs that caused them to worry about how the homeschooled children were being cared for.

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One of the children, Devonte Hart, gained national attention in 2014 when he was photographed with tears in his eyes hugging a Portland police officer at a protest.

Nov. 25, 2014 file photo provided by Johnny Nguyen shows Portland police Sgt. Bret Barnum and Devonte Hart, 12, hugging at rally in Portland, Ore., in support of protests in Ferguson, Mo.; picture of him hugging the white police officer during the protest went viral AP

CBS affiliate KOIN-TV reports that singer Jenni Price of the band Acoustic Minds wrote the song "Quicksand" that was inspired the famous photo. When Price asked her friend Jennifer Hart to help make a video for the song, she said the family was reluctant.

"They had been laying very low due to the backlash of the photo," she told KOIN in an email. "They had gone into hiding and just became a bit recluse due to death threats they had received."

Price wrote she "had never met a family like this ...They did not have TV, they did not use cellphone, they did not have technology in ways like children are glued. Instead their home was filled with books, musical instruments, artistic equipment like paint and crayons and markers and huge construction paper for art projects, their yard was open and a large part of it was a garden."

But neighbors Bruce and Dana Dekalb saw something different.

"Their daughter is telling us, 'Please, please, please,' begging us not to go back. They're abusing her," said Dana Dekalb. "And then Devonte coming over here and telling us he's being starved to death."

This March 20, 2016 photo shows Hart family of Woodland, Wash., at a Bernie Sanders rally in Vancouver, Wash. Authorities in Northern California say they believe all six children from a family were in a vehicle that plunged off a coastal cliff. Tristan Fortsch/KATU News via AP

The Dekalbs say recent cries for help from the Hart children prompted them to call Child Protective Services.

"I was trying to help them and protect them and this is the result," said Dana.

Price told KOIN that it was hard for her to reconcile what she knew about the Hart family and the fact that neighbors said they were forced to call Child Protective Services.

"This family exemplified the hope, acceptance, genuine will of unconditional love for ALL beings. I am a better human for knowing them. I am honored to have got to spend the time that I did with them," she wrote.