They were the portrait of a modern family: a married female couple and their six adopted children. And in 2014, they were thrust in front of the world for all to see.

One of those children — Devonte Hart, who is black — was photographed hugging a white police sergeant in Portland, Ore., during a 2014 demonstration to protest police violence. In the photograph, Devonte clung to the officer, a mix of fear and anguish in his tearful eyes.

But the intense news media coverage that followed may have been the reason the Hart family decided to flee to Washington state, authorities said on Wednesday.

Then, the unthinkable: The family’s sport utility vehicle plunged off a 100-foot cliff in Northern California and was discovered on Monday — upside down, engulfed by the waves of the Pacific Ocean.

Both parents, Jennifer and Sarah Hart, were found dead inside the SUV; three of their children were discovered dead outside it; and the three other children, including Devonte, were still missing on Wednesday evening and feared dead, law enforcement officials said.

“We have every indication to believe that all six children were in there; however, only three bodies have been recovered,’’ said Sheriff Tom Allman of Mendocino County. “We have no evidence and no reason to believe this was an intentional act. Certainly people are wondering what caused this.’’

Still, authorities did not discount the possibility that some of the children may have been staying with friends.

At a news conference on Wednesday, Allman conceded that many questions remain: When did the accident, as he called it, occur? Why did the SUV drive across at least 75 feet of dirt before plummeting into the ocean? Why weren’t there skid marks?

Allman said his office knew of no witnesses.

In the meantime, troubling reports about the family have emerged.

Washington state Child Protective Services learned on Friday of allegations of abuse against the Harts and tried to make contact with them that day, but no one answered when its employees visited their home, Norah West, a spokeswoman for the state’s Department of Social and Health Services, said on Wednesday.

West said that Child Protective Services had opened the inquiry because of “allegations of abuse or neglect in the home.’’

She said the children’s agency made two subsequent attempts to establish contact with the family, visiting the home again on Monday and Tuesday, but was unsuccessful. A spokesman for the Clark County Sheriff’s Department in Washington state said he was not aware of any previous interactions with the family.

A neighbor of the Harts in Woodland, Wash., Dana DeKalb, told NBC affiliate KGW that Devonte, the child from the 2014 photograph, had recently begun venturing over to her home to ask for food, sometimes several times a day.

According to DeKalb, Devonte said his mothers sometimes withheld food from the children as punishment and didn’t allow them outside.

DeKalb said she was the one who brought the family to the attention of Child Protective Services. She told KGW that when an employee from the children’s agency visited on Friday, the Harts refused to answer the door, and that the family left only hours later. DeKalb did not immediately respond to a telephone message on Wednesday night.

Publicly available records show that Sarah Hart had lived in Minnesota for years before eventually moving to West Linn, Ore., and then Woodland, Wash. Court records show that a woman with her name and age was convicted of misdemeanor domestic assault in Minnesota in 2011.

Investigators identified the bodies of Jennifer and Sarah Hart, both 38, of Woodland. By Wednesday, coroner’s officials had also identified the bodies of the three children: Markis, 19; Jeremiah , 14; and Abigail, 14. Authorities say the three missing children are Devonte, 15; Hannah, 16; and Sierra, 12.

In 2014, Devonte was photographed at a demonstration in Portland, one of many protests across the country of a grand jury’s decision not to bring criminal charges against Darren Wilson, the police officer who fatally shot Michael Brown in Ferguson, Mo. Devonte, who was then 12, had been holding a “Free Hugs’’ sign, and Sergeant Bret Barnum approached him to ask why he was crying.

The photograph of the two embracing, which was first published by The Oregonian newspaper, ricocheted around social media and was featured by major news media outlets.

In an interview at the time with The Oregonian, Barnum said the boy told him that he was sad “about the protests, kind of about national events.’’

“I just kind of sighed,’’ he recalled, “and said, ‘I’m sorry.’’’