CNN affiliate KING has more on this story.
(CNN) -- The body found Saturday in a fortified bunker in Washington state is believed to be a murder suspect who had been hiding inside, the King County Sheriff's Office said.
A sheriff's SWAT team blew a hole in the roof of the hideout with explosives and saw what they believe to be the body of Peter Keller. It appeared he died of a self-inflicted gunshot wound, the sheriff's office said.
"They believe the person has been dead for some time. There's a great deal of blood and a pistol nearby," Sheriff Steven D. Strachan said.
A bomb disposal unit cleared the bunker to ensure there were no explosives or booby traps, officials said.
Deputies earlier said they had Keller, 41, contained inside the bunker.
Authorities fired tear gas late Friday into the bunker, set into the Cascade foothills about 25 miles east of Seattle. It was unclear whether the gas went deep enough to have any effect.
Keller had not been seen since Sunday following a fire at his home, where the bodies of his wife and teenage daughter were discovered.
His standoff with authorities began Friday after investigators found evidence that led them to the bunker near Rattlesnake Ridge Trail, according to the sheriff's office.
Authorities didn't immediately send deputies in because of safety concerns.
Investigators do not have a clear motive for the slayings, according to Sgt. Cindi West of the King County Sheriff's Office.
Keller, who did not have a criminal record, was described as a survivalist by some relatives, West said.
"We gathered he had a doomsday attitude ... family and friends have indicated he thought the world was going to end at some point," West said.
Keller likely had plenty of arms and supplies in the bunker, officials said.
Clues to Keller's whereabouts came while investigators were processing evidence at his house, authorities said. People in the area also reported seeing Keller's pickup truck near the trailhead.
"This isn't a hole in the ground. This is a large built-up structure," Strachan said of the bunker. "But hidden. It took some time to find it. In fact our tactical team smelled the wood smoke coming before they actually saw it."
Strachan said Keller's house nearby was set afire Sunday after the slayings, but it failed to spread beyond the kitchen. Authorities found a hard drive with photos, he told CNN Seattle affiliate KING.
One photo was enhanced and it aided in the search for Keller, who authorities said had been building the bunker for at least eight years.
The sheriff's office this week obtained an arrest warrant for Keller stipulating two counts of first-degree murder and first-degree arson.
CNN's Phil Gast and Kara Devlin contributed to this report.