Anthony Garver's parents called authorities to say their son was at their house in a wooded, mountainous area in the Spokane Valley, Gregory said. Officers got the information Thursday night, but Garver was gone when they arrived.
"We immediately sent resources to lock down the area and conducted an extensive search in conjunction with the U.S. Marshals' office," Gregory said. "There were two helicopters, four canines and several other resources deployed in the search. We did not locate him."
Gregory said Garver may be difficult to find because he's comfortable in the woods.
"He has stayed out in the wild for weeks or months in the past," he said. "We don't know if he's camping out somewhere nearby or if he has left the area. He is believed to be armed and very dangerous. We don't have specific information that he has weapons but in the past he has been armed."
Garver was first caught in the summer of 2013 for allegedly tying a woman to a bed with electric cords, then stabbing her to death. He was at a psychiatric hospital after being found not competent to stand trial.
Garver, 28, and Mark Alexander Adams, 58, escaped Wednesday from Western State psychiatric hospital in Lakewood, but Adams was arrested Thursday in Des Moines, about 15 miles outside Seattle.
Garver bought a bus ticket Wednesday night from Seattle to Spokane under the alias John Anderson, authorities said.
"We have stills of him purchasing the ticket," said Lt. Chris Lawler, spokesman for the Lakewood Police Department.
Pair 'got a considerable head start'
Both Garver and Adams had been committed for mental illness treatment to Western State, described on its website
as "one of the largest psychiatric hospitals west of the Mississippi," with more than 800 beds.
The two were seen in the facility's dining hall around 6 p.m. Wednesday, according to Lakewood police.
They weren't noticed missing until about 1½ hours later, after having gotten out -- likely through a loose window, which roommates told police was manipulated over five months to open enough to escape from, according to Lakewood police spokesman Chris Lawler.
From there, Garver and Adams apparently walked off together.
"They got a considerable head start," Lawler told CNN affiliate KIRO-TV
Adams took a bus from Lakewood to Federal Way, Washington, arriving there around 10:30 p.m; he asked how to get to Seattle-Tacoma International Airport, police said on Facebook. Lawler credited a tipster who'd seen media coverage of the escape with spurring authorities to check surveillance footage from there.
"That makes it very difficult to run, when the public is paying attention," the police spokesman told reporters Thursday.
Considered not competent to stand trial
The two men had been at Western State Hospital since February 2015, but they'd been on authorities' radar long before then. Both were found not competent to stand trial.
Adams was arrested for second-degree assault/domestic violence in 2014 for choking someone, according to Lawler.
And Garver -- who sometimes uses the last name Burke -- was wanted on several outstanding warrants in July 2013 when he was charged with murder in the killing of Phillipa S. Evans-Lopez, 20.
Detectives linked Garver to the woman's death based on evidence from the scene and surveillance video footage showing the two of them together in the days before her death, according to the Snohomish County, Washington, Sheriff's Office
Lawler, the Lakewood police spokesman, said Garver has ties to Spokane. But it's not known if went there.
He urged the public to be on alert but not to try to approach Garver.
"If you just look at the crime itself," Lawler said of Evans-Lopez's killing, "obviously, we don't want someone who has done something like that free."