(CNN) -- A Washington state man wanted in the killings of his wife and daughter was believed to be holed up Friday evening in a fortified bunker about 25 miles east of Seattle, authorities said.
SWAT and other teams deployed tear gas into the hillside structure in an effort to smoke out suspect Peter Keller, said Sgt. Cindi West of the King County Sheriff's Office.
"We do believe somebody is in there. We heard something going on, but nothing lately," West said. "We can't send people in there because of safety."
The homemade bunker is outside North Bend near Rattlesnake Ridge Trail, according to the King County Sheriff's Office.
Keller, 41, is not believed to have a previous criminal record. Investigators do not have a clear motive for the slayings, according to West.
"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.
Some relatives have termed Keller a survivalist, she added.
Keller was believed to be well armed. "We know he in the past has had a number of rifles, scopes and handguns. He purchased some kind of bulletproof vest," West said.
Clues to Keller's whereabouts came during the processing of the crime scene at his house, authorities said. Citizens 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," Sheriff Steven D. 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.
"We believe he has taken pictures from 2004 to the present day," said West.
She said she did not know the precise size of the bunker, made partially of earth and logs.
"We believe it is very large," the spokeswoman said. "He has had plenty of time to work on it."
The sheriff's office earlier this week obtained an arrest warrant for Keller, stipulating two counts of first-degree murder and first-degree arson.
The bunker was found early Friday about 800 yards off the trail. It's possible the bunker has an escape hatch or door, officials said.
The slaying victims were identified as Keller's wife, Lynnettee, and daughter, Kaylene, believed to be either 18 or 19.
According to West, Keller works with a company that refurbishes and sells computers.
SWAT and other teams weren't forcing the situation because of the possible danger involved of rushing inside. And Keller is likely to be well-supplied, officials said.
"There is no urgency. We have him contained," West said.