NORTH BEND — SWAT team officers prying open Peter Keller's elaborate underground bunker Saturday morning worried the heavily armed survivalist might try to ambush them or blow them up with a booby trap.

Instead, after using explosives to loosen the lid to his 20-foot-long, two-story hideout, they found his body, a pistol and a pool of blood, said King County Sheriff Steve Strachan.

Authorities believe Keller shot himself in the head, though they aren't sure when.

Officers discovered and surrounded his bunker Friday afternoon by following his footprints and a whiff of smoke a mile east of the Rattlesnake Ridge trailhead. SWAT team members surrounding the bunker Friday heard popping noises that could have been gunshots.

Keller, 41, had been charged earlier in the week with shooting and killing his wife and daughter last Sunday in their North Bend home, then setting the house on fire.

His daughter, Kaylene Keller, 19, and her mother, Lynnettee Keller, 41, both died from gunshots to the head. Their bodies were found in their bedrooms.

Court documents described Keller as a loner who had a survivalist mentality and had been stockpiling supplies in the woods. Keller worked in a computer-refurbishing business and was an avid outdoorsman who often took long hikes on weekends.

His hideout was built into a sheer hillside, with several entrances and ladders, officers said.

"This isn't a hole in the ground. It's an elaborate structure," Strachan said Friday.

A sheriff's department spokeswoman said Keller worked eight years building his hideout.

Inside, the bunker held 13 guns and shelves filled with neat stacks of ammunition, a stove, a water jug, sealed plastic containers, bags of concrete, PVC pipe, what deputies described as a small trailer, some cans of gasoline, buckets and a ventilation system.

Keller's daughter had told her boyfriend that her father had been gathering supplies and preparing for the "end of the world."

News of Keller's death came suddenly, just after law enforcement had replaced a tired, overnight crew with fresh officers.

Authorities had searched for nearly a week before they found Keller, and expected the standoff might go on for days outside of the underground fortress.

Sheriff's deputies shot tear gas into the bunker Friday, but there was no response. Overnight they believed there were lights going on and off inside the bunker.

Strachan said officers used tools and a cord of explosives Friday night to loosen the earth around the outside of the bunker.

They were then able to pry away logs supporting the bunker — all the while wondering whether it was booby-trapped with explosives and knowing Keller might be inside and armed.

Around 10 a.m. Saturday, officers set off a second round of explosives and were able to peer inside the upper and lower chambers of the elaborate bunker.

They reported seeing the body, the pistol and the pool of blood, Strachan said.

An arrest warrant issued Wednesday accused Keller of two counts of first-degree murder and one count of first-degree arson.

He had withdrawn $6,200 from a bank account last week and told one of his co-workers at a computer-refurbishing store in Preston that he might not return, according to court documents.

Trained trackers found Keller's footprints Thursday, and then the whiff of wood smoke gave away the bunker's location Friday afternoon.

The terrain was so rugged that four SWAT team members had to go to the hospital for dehydration and exhaustion after navigating the heavily wooded and muddy area around the two-story bunker. One officer sprained an ankle.

After they discovered the body, officers rappelled in from a helicopter to investigate the inside of the bunker, checking the hideout for booby traps and explosives.

They planned to remove Keller's body by helicopter, as well. A spokeswoman said the bunker will likely be demolished after the investigation is complete.

Christine Clarridge: 206-464-8983 or cclarridge@seattletimes.com. This story contains information from The Associated Press.