WOODLAND, Wash. -- The two women and their six adopted children traveled to festivals and events, offering free hugs and promoting unity, friends said. They raised animals and grew vegetables and last year moved onto a piece of land in rural southwest Washington, a dream of theirs.

The Hart Tribe, as they were known, also took spontaneous road trips to hike or camp, and friends believe they may have been on one of those adventures when their SUV plunged off a scenic California highway. Authorities don't know what caused the crash but they believe all six kids were inside the car and none were wearing seat belts, reports CBS News' Anne-Marie Green.

"We know that an entire family vanished and perished during this tragedy," said Mendocino County Sheriff Tom Allman on Wednesday as he appealed for help retracing where the family had been before the vehicle was found Monday.

Sarah and Jennifer Hart with their 6 children in an undated photo KOIN-TV

According to police, the SUV pulled off on a dirt turnout and then traveled about 75 feet before going over the cliff's edge, and into the Pacific Ocean. The 100-foot drop killed Jennifer and Sarah Hart, both 39, and their children Markis Hart, 19; Jeremiah Hart, 14; and Abigail Hart, 14. Hannah Hart, 16, Sierra Hart, 12, and Devonte Hart, 15, have not been found.

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Friends described the married couple as loving, inspiring parents who promoted social justice and exposed their "remarkable children" to art, music and nature. Devonte Hart drew national attention after he was photographed hugging a police officer during a 2014 Ferguson protest in Oregon. But neighbors said they saw signs that caused them to worry about how the home-schooled children were being cared for.

Next-door neighbors told CBS affiliate KOIN the Harts almost never left home and that signs of trouble started to become apparent. Bruce and Dana DeKalb said they called child services Friday because they were concerned about Devonte, now 15, who they said had been coming over to their house in the past week asking for food.

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 Johnny Huu Nguyen / AP

Dana DeKalb said Devonte approached her about a week ago and told her that his parents "weren't feeding them" and were "punishing them by withholding food." She told CBS affiliate KOIN the child at first just asked for a little, then more and more.

He came over almost every day for a week, and asked her to leave food for him in a box, she said.

"He was asking that we not tell his mom, to hide it and put it by the fence so he could get to it," Dana DeKalb told KOIN.

They described another time in which a little girl came over covered in blackberry thistle and asked for help because, they said, she was afraid to go back to her home, KOIN reports.

The couple told KOIN of another incident in which a girl came over early in the morning and said she didn't want to go back home.

"She wanted us to take her to Seattle because they weren't treating her right," Bruce DeKalb told the station. "'Don't make me go back,'" he said the girl said.

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 told KOIN a 12-year-old girl looked to be about 7 and had front teeth missing. All the children appeared very thin and small, they said.

The concern prompted the call to Child Protective Services last Friday, and state officials responded when they knew the Harts were home, the couple said. Later, they noticed their car was missing.

"I was trying to help them and protect them and this is the result. It's not easy," Dana DeKalb told the station. "That's not how I thought it was going to end."

The California Highway Patrol has not determined why the vehicle went off an ocean overlook on a rugged part of coastline. A specialized team of accident investigators was trying to figure that out, Allman said.

"We have no evidence and no reason to believe that this was an intentional act," he said, adding that the scene was confusing because "there were no skid marks, there were no brake marks" at the roadside turnout where the vehicle went over.

"This is a tragic accident of a magnitude that cannot be measured," said Zippy Lomax, a photographer who knew the Harts.

"They were really radiant, warm, adventurous inspiring people. They were always on some grand adventure, and the kids were living this life that was kind of like this dream," Lomax told The Associated Press. "The family was this very self-supporting unit that was impossible to miss. When they showed up to an event, they made an impression. They shattered a lot of norms and they did not shy away from controversy or adversity."

The Harts, who went to events such as rallies for presidential candidate Bernie Sanders, often showed up in matching T-shirts.

The family was often seen marching together or going to family-friendly music festivals. Lomax told KOIN she first met the family at the Beloved Festival in Tidewater in 2012 and noted their energy and charisma right away.

"They were that really bright kind of presence," Lomax said. "It was pretty hard to miss them. Any event that I was at where they were, if I had a camera, I was attracted to that."

Lomax told KOIN the parents appeared to do everything possible to give their kids a stable life.

"Jen and Sarah really were the kind of parents that I think the world desperately needs," Lomax said.

The Harts moved to Woodland, Washington, a small city outside Portland, in the spring of last year, partly overwhelmed by the media coverage. The multi-racial family also received death threats, Ribner said.

The family had a recent visit from state child protective services, Clark County sheriff's Sgt. Brent Waddell told AP.

Washington state child protective services opened an investigation Friday and tried to make contact with the family three times since then, but weren't able to reach them, said Norah West, a spokeswoman with the state Department of Social and Health Services. The agency had no prior history with the family, she said.

In 2011, Sarah Hart pleaded guilty to a domestic assault charge in Minnesota. Her plea led to the dismissal of a charge of malicious punishment of a child, online court records say. According to court records, a teacher saw bruises on the couple's 6-year-old daughter. The girl told the teacher, "mom hit me."

Sarah Hart allegedly admitted to police she "let her anger get out of control."

Max Ribner, who has known the family since 2012, said allegations from neighbors don't square with what he knows about the Harts.

"They are beautiful examples of opening arms to strangers, helping youth, supporting racial equality," Ribner, who lives in Portland, told the AP. "They brought so much joy to the world. They represented a legacy of love."

Bill Groener, 67, was a next-door neighbor of the Harts when they lived in West Linn, Oregon, and said the kids stayed indoors most of the time. He said the family didn't eat sugar, raised their own vegetables, had animals and went on camping trips.

"There was enough positive there to kind of counteract the feeling that something maybe wasn't quite right," Groener said.