NORTH BEND, Wash. â€"  Washington police believe a body found near a pistol and a pool of blood inside an underground bunker is that of murder suspect Peter Keller, Fox News confirms. 

Authorities used an explosive to breach the roof of the heavily fortified bunker, which allowed enough access for the officers to enter. 

Authorities discovered a body inside which they say appeared to be Keller, and it appeared as though he died of a self-inflected gunshot wound, according to a King County Sheriff's press release. 

Police had surrounded the rugged underground bunker believed to belong to the Washington state murder suspect and had ordered negotiators to scene to try to lure its occupant outside.

King County Sheriff's Sgt. Cindi West says a team of the department's hostage negotiators were dropped Saturday morning by helicopter into the Cascade Mountain foothills east of Seattle where the 41-year-old  was believed to be holed up.

West says the negotiators were trying to contact whoever is in the bunker by bullhorn and other means. SWAT teams reported having seen lights go on and off inside

Keller is suspected of killing his wife and teenage daughter before setting his house on fire in an attempt to cover it up. Authorities maintained a perimeter early Saturday around an elaborate, underground bunker where he might be hiding in the woods of Washington state.

SWAT teams had surrounded the bunker Friday, and almost four dozen officers were at the scene at Rattlesnake Ridge, south of North Bend, where Keller is thought to be holed up.

Police pumped tear gas into the structure in the Cascade foothills east of Seattle and said they "heard and saw movement" in the structure.

Sheriff's officials said later Friday they weren't sure the gas penetrated deep enough to reach the person inside. They also believed the person inside likely has a gas mask.

Efforts were being made to communicate with the individual via a megaphone but cops had so far received no response.

"It could very well be that he's waiting for us to come in and get him. This is a very fluid and dangerous situation," Sheriff Steve Strachan said.

Strachan said that the standoff could last hours, days or even weeks.

According to court documents, Keller had been preparing for "the end of the world" and had stockpiled weapons and food in the woods. He was also described by people who knew him as a "survivalist" with a "distaste for authority."

Keller owned handguns, rifles, silencers and body armor, one of his colleagues at an IT firm told detectives.

Photos of the bunker "don't do it justice," SWAT officers told sheriff's spokeswoman Sgt. Cindi West.

"They said the fort appears to be amazingly fortified," she said.

It was believed that Keller had been building the bunker for some eight years. West said that police managed to locate the well-hidden structure from photographs found in his home.

SWAT teams began a systematic search of the area at 5:00 a.m. local time Friday, the Snoqualmie Valley Record reported. It was not immediately known what time they found the bunker.

The bunker is off trail at Rattlesnake Ridge and witnesses reported seeing Keller's pickup truck in the area in recent weeks.

Keller was charged Wednesday with two counts of first-degree murder and a single count of arson.

His wife Lynnettee Keller, 41, and teenage daughter, Kaylene, 19, were found shot dead inside a burning home in North Bend, about 30 miles southeast of Seattle, on Sunday.

The Associated Press and Newscore contributed to this report.