The Department of Social and Health Services says Zamora was removed under a 2010 law that allows the transfer of patients who pose a safety risk.
Zamora will now be housed in a "special offender unit" at the Monroe Correctional Facility.
"Higher security, much more secure perimeter," said Scott Frakes, deputy director of prisons. "Each of the buildings has a higher security levels, much higher staffing, security staffing level."
Zamora did not resist the transfer and was compliant, officials said.
On Sept. 2, 2008, Zamora killed neighbors in the small Skagit County town of Alger, construction workers, a driver on Interstate 5, and Skagit County Sheriff's Deputy Anne Jackson.
Zamora pleaded not guilty by reason of insanity to two murders and guilty to the remaining four, getting four life sentences as a result. His plea bargain stipulated that he stay at Western State until a court ordered him moved to prison. Zamora had been at Western State for three years.
But being housed at the prison is considered a lot less expensive than Western State, where two state corrections SWAT team members stood guard over Zamora 24 hours a day at a cost of $1 million a year. Workers at the state hospital applaud the move because of the dangerousness of Zamora.
Psychiatric attendant Patrick McDonough reportedly was attacked by Zamora and was seriously injured.
"The risk to the staff is real and it's a daily threat to them," said Carol Dolitch, president of the Washington Federation of State Employees.
DSHS will maintain Zamora's treatments and a review of his status will take place within 90 days. The state is expecting legal challenges to the new law that allowed the shift from a mental institution to a prison.