Terry Vance Garner, 69, never returned after he set out to feed his animals last Wednesday on his farm near the Oregon coast, the Coos County district attorney said Monday.
A family member found Garner's dentures and pieces of his body in the hog enclosure several hours later, but most of his remains had been consumed, District Attorney Paul Frasier said. Several of the hogs weighed 700 pounds or more.
It's possible Garner had a medical emergency, such as a heart attack, or was knocked over by the animals, then killed and eaten, Frasier said, adding that at least one hog had previously bitten Garner.
The possibility of foul play is being investigated as well.
"For all we know, it was a horrific accident, but it's so doggone weird that we have to look at all possibilities," Frasier told The Register-Guard.
A pathologist was unable to identify a cause or manner of death, the newspaper reported. The remains will be examined by a forensic anthropologist at the University of Oregon.
Terry Garner was "a good-hearted guy" who cared for several huge adult sows and a boar named Teddy, said his brother, Michael Garner, 75, of Myrtle Point.
Piglets were typically sold to local 4-H kids.
"Those animals were his life," Michael Garner said. "He had all kinds of birds, and turkeys that ran all over the place. Everybody knew him."
Michael Garner said one of the large sows bit his brother last year when he accidentally stepped on a piglet.
"He said he was going to kill it, but when I asked him about it later, he said he had changed his mind," the brother said.
Domestic hogs are not typically known to be as aggressive as their feral cousins, but "there is some degree of danger associated with any animal," John Killefer, who heads the Animal and Rangeland Sciences Department at Oregon State University in Corvallis, told the newspaper.
While pigs "are more omnivorous than other farm animals, (such as) cows," Killefer called the case highly unusual.
Most hogs are raised until they reach a market weight of between 250 and 300 pounds, while breeding female pigs rarely weigh more than 400 pounds, Killefer said.