Howard Kuljian and his Eureka family were out for a walk on a damp, overcast morning at Big Lagoon beach in Humboldt County, playing fetch with their dog Fran as 10-foot surf churned the water just feet away like a washing machine.

Signs near the beach warned of "sneaker waves," the kind that suddenly roar ashore.

Kuljian tossed a stick that took the dog down to the water's edge, and in an instant, authorities said, a wave swallowed it, setting off a nightmarish scramble.

"Everything kind of snowballed from there," Coast Guard Lt. Bernie Garrigan said.

Kuljian's 16-year-old son, Gregory, ran to save the dog, only to be captured by the surging surf himself. Kuljian, 54, followed, and then his wife, Mary Scott, 57. On shore, their 18-year-old daughter, Olivia, and Gregory's girlfriend could only watch.

Both parents' bodies were later recovered, but the boy -- presumed dead -- is still missing off the beach just south of Orick.

The dog eventually made it back to shore.

News of Saturday's tragedy shocked many in the Eureka and Arcata communities.

Kuljian was a fire ecologist at Six Rivers National Forest, a second career and dream job he got after earning a graduate degree in 2010 from Humboldt State University's wildland fire laboratory.

His master's thesis on sudden oak death was "cutting edge" and published widely, said Morgan Varner, a former Humboldt State professor now with Mississippi State University's forestry department.

"He was the first researcher to quantify the real threat not only for sudden oak death but also the threat over the West with mountain pine beetles," Varner said.

Scott, a nurse, worked for the county health department and was a devoted member of the Humboldt Community Breast Health Project.

The couple were avid runners and outdoors people. Their deaths leave a large hole in the Arcata community, Varner said.

"There's no one that wouldn't say they were both kind and gentle," Varner said.

Students at Arcata High School on Monday wore green in Gregory's memory.

By late afternoon, more than 1,300 people "liked" a Facebook page set up by the teenager's friends called "Wear Green for Geddie" -- using his nickname. Dozens tweeted tributes at #WearGreenForGeddie.

"I will always remember him no matter how long," Emmalaya Owen wrote on the Facebook page. "Especially how he was such an upbeat happy person or how he tried to put up 'Be Happy' propaganda posters he drew around school."

Others were trying to come to terms with the deaths. His sister graduated last year.

"He was just a friendly guy, and everyone who knew him liked him, and his family was very close," said Day Robins, a senior.

She said Gregory and his family were active in school athletics and sailing.

At Big Lagoon, a short drive from Arcata, signs posted near the parking lot warned beachgoers not to turn their back to the surf and to pay special attention to sneaker waves.

"Because the beach is designed that way, when that 10-foot wall breaks, it surges up on the beach and surges back really fast," the Coast Guard's Garrigan said. "It's like a cyclical washing machine."

As the family walked along the beach, Howard Kuljian threw the stick and the dog gave chase, said Dana Jones, a state parks district superintendent.

Seeing his son in the water, Kuljian leapt to action and disappeared into the frigid water.

Gregory managed to pull himself back onto the sand, but after realizing his father was drowning, both he and his mother went in to save him.

As Olivia and the girlfriend watched the water in horror, a nearby bystander called police. By the time help arrived, it was too late. Jones said the officer wasn't able to get to the family members because of the high surf.

Garrigan said the search for the teenager was stopped because a person without a wetsuit could not survive for long in the cold surf.

The Coast Guard dispatched a helicopter and two boats to search for the boy, but thick fog made it difficult.

"When there is shorebreak like that, you don't even have to go into the water to be pulled into the sea," Jones said. "It's a reminder to be real careful around the ocean."

This story was compiled from reports by Staff Writer Julie Johnson and the Associated Press.