WILLITS, California -- An Alaska man camping at the coast awoke to the sound of an engine revving and tires squealing against gravel at the highway turnout where authorities found five bodies near an overturned SUV the next day.

The man next heard a loud noise but when he went to survey the cliff in the dark, he saw nothing. Recalling what happened days later to investigators, he said he thought he heard someone call for help but wrote off the noise as coming from a seal, said California Highway Patrol Officer Jay Slates.

The account ended three hours of revelatory testimony about the March 2018 crash that killed the eight members of a Southwest Washington family, including five children and their 19-year-old brother. The second day of the coroner’s inquest into their deaths has provided the most insight yet about how the family of eight spent their final hours hundreds of miles from home.

Driver Jennifer Hart, her wife, Sarah Hart, and their children, Markis, 19, Hannah, 16, Devonte, 15, Jeremiah, 14, Abigail, 14, and Sierra, 12, all died in the crash, according to authorities. Devonte's body has never been found.

An officer trained to analyze crash scenes said that based on all the evidence his team collected, including readings from the SUV’s “black box” computer, they reached an inevitable conclusion about the cause of the crash: intentional.

Computer readings showed the vehicle idled, then accelerated at full throttle over a protective grass berm and off the cliff. Within two seconds, the vehicle landed upside down at the base of the cliff.

“When you’re at a cliff edge with your family inside, how often do you apply 100 percent throttle?” asked Officer Timothy Roloff.

A jury of eight women and six men could begin deliberating as early as this afternoon to determine the manner – accident, suicide, natural causes or death at the hands of another -- in which each family member died. Slates’ testimony will resume Thursday afternoon. One more investigator remains on the witness list after him.

A Garmin GPS recovered weeks after the crash allowed police to piece together an incredibly detailed timeline of the family’s journey from their Woodland, Washington home to the Mendocino Coast, Slates said. Stops included a Walmart in Longview, where authorities believe Jennifer Hart bought the generic version of Benadryl, sold by Walmart under the brand name Equate, he said. Police found diphenhydramine-containing Equate medicine in liquid and pill forms in the wreckage.

Sarah Hart must have consumed at least 42 doses before the crash, based on toxicology tests, Slates said. The three children whose blood could be tested must have consumed between nine and 19 doses, he said.

Police learned Jennifer and Sarah Hart often gave their adolescent children Benadryl on long drives “just so they would sleep,” Slates said.

Jennifer Hart had alcohol in her system, tests showed. Friends and family members told investigators she rarely drank and never consumed a full glass of wine.

But at the time of the crash, her blood alcohol level of 0.102, above the legal limit of 0.08, indicated she had drunk the equivalent of at least five beers, Slates said.

During four years they lived in Oregon and their subsequent time in Washington, the family often trekked across the country to national parks and music festivals with Jennifer Hart at the wheel of their GMC Yukon. They told friends that they hoped to some day visit the Mendocino Coast but had no immediate plans to do so, Slates said.

Data from the Hart SUV’s GPS, which stored information from as far back from 2010, show the family drove south from Woodland at 8:30 p.m. on March 23, the same day a child welfare case worker went to their home to investigate reports that the children weren’t being fed.

The case worker accidentally responded to the neighbor's home, and saw a GMC Yukon pull into the Hart family driveway, Clark County Deputy Adam Beck said. But no one answered the door.

The Harts drove north on Interstate 5 and at some point turned west toward the coast, Slates said. Before they reached U.S. 101, the coastal highway, they pulled into the Walmart, where Jennifer Hart spent the next 18 minutes and purchased the store-brand Benadryl.

The SUV kept driving south toward California, stopping several times, first for almost two hours at Dismal Nitch, a turnout on a southern Washington highway near the mouth of the Columbia River, Slates said.

They continued on to a site near Tillamook, where they parked for more than three hours, then drove into Newport. A surveillance video shows Jennifer Hart quickly go into a Fred Meyer and buy something, but police aren’t sure what, Slates said. Video of the parking lot isn’t clear enough to make out anything about the vehicle’s occupants.

The family kept driving south, stopping for short stretches twice more in Oregon and then a few more times in California. Their vehicle then turned toward the coastal highway leading to Fort Bragg, where they passed the scenic lookout that Jennifer Hart would eventually drive off.

When they arrived in Fort Bragg at 7:19 p.m. March 24, someone turned the GPS device off, Slates said.

Surveillance video and cell phone pings helped police reconstruct the next day, including footage of Jennifer Hart at a local Safeway store that officials released soon after the crash.

After Jennifer Hart bought groceries that morning, Sarah Hart went to a nearby Dollar Tree and bought toothbrushes, hairbrushes, a single sleeping mask and other personal items, Slates said.

Footage from a gas station also captured the family, once as they drove south out of town and again as they headed back north. A cell phone belonging to the family pinged for a final time at 9 p.m. at Cleone, a small town north of Fort Bragg, Slates said.

Two hours later, the man from Alaska heard a vehicle pull into the coastal site where he was camping with his wife, Slates said. The man looked out of his and saw a “larger vehicle” similar to the Harts’ SUV, Slates said. The man didn’t notice anything amiss and fell asleep.

Some time later, he heard the engine revving, Slates said.

Roloff, the crime scene investigator, said a computer that tells the air bag when to deploy captured the final seconds of the vehicle’s movements. Through that data, investigators learned that the vehicle was stopped at the lookout point, then hit speeds up to 20 mph before they believe it launched into the air. Once the vehicle started moving, the brakes were never hit.

Seconds may not sound like much, he said, but it only takes seconds for a crash to occur.

“Our analysis of the data was that this was consistent with this being an intentional act,” Roloff said.

This is a developing story and will be updated.

-- Molly Young

myoung@oregonian.com