The man's daughter called police Friday evening after finding her father's body inside the garage at the home, located in the 15000 block of NE 192nd Street, said a King County Sheriff's Office spokesperson.
The man, who has not been identified but is believed to be in his 70s, had obvious head trauma, according to the King County Sheriff's Office. His death originally was called "suspicious," then was ruled a homicide Saturday morning.
Deputies would not comment on why investigators ruled the death a homicide, but did say that there's enough things that don't add up.
"We're really just at the very beginning of the investigation," a deputy said. "We have more questions than answers."
Sheriff's officials would not release the victim's name, but property records show the house is owned by 74-year-old Earl Cossey.
When DB Cooper hijacked a passenger jet from Portland, Ore., to Seattle in 1971, demanding $200,000 and four parachutes, it was Cossey who packed the chutes.
After asking to be flown to Mexico, Cooper jumped out somewhere near the Oregon line. Despite intensive searches, no sign of Cooper ever emerged.
Investigators doubt he survived and have never been able to determine his true identity. But a boy digging on a Columbia River beach in 1980 found three bundles of weathered $20 bills - Cooper's cash, according to the serial numbers.
The parachutes provided to the skyjacker came from an Issaquah skydive center which had recently purchased them from Cossey. The one Cooper apparently used was a military-issue NB6, nylon, 28-foot with a conical canopy.
Over the decades, as parachutes were sometimes discovered in the area of Cooper's jump, the FBI turned to Cossey to ask if they were the real thing.
"They keep bringing me garbage," Cossey told The Associated Press in 2008, after the FBI brought him a silk parachute discovered by children playing at a recently graded road in Southwest Washington. "Every time they find squat, they bring it out and open their trunk and say, 'Is that it?' and I say, 'Nope, go away.' Then a few years later they come back."
That didn't keep Cossey from having fun at the expense of reporters who covered that discovery. He told some who happened to call him on April Fools' Day that year that the chute was, in fact, Cooper's.
One reporter called him back and angrily said he could get fired for writing a false story, Cossey said. Another said the newsroom was amused by the prank.
"I'm getting mixed reviews," Cossey said. "But I'm having fun with it. What the heck."