Police are looking for Michael "Chad" Boysen, 26, calling him a suspect in the deaths of the 82-year-old man and 80-year-old woman Friday night or early Saturday at their home in the Fairwood area of Renton.
Boysen "is considered an extreme danger to the public and police," the King County sheriff's office said.
Detectives believe he's trying to find weapons. He had been searching the Internet for "gun shows" across the Northwest and Nevada, the sheriff's office said.
Boysen is 5-foot-10, 170 pounds with hazel eyes. He may be driving the red, 2001 Chrysler 300, Washington license 046XXU.
Boysen had been in prison since 2006 on three robbery convictions in King County, said Judy Feliciano with the Washington Department of Corrections. He was released Friday from the prison at Monroe and was supposed to check in with a community supervision officer within 24 hours, she said.
Investigators had no leads Monday, said sheriff's spokeswoman Sgt. Cindi West.
Autopsies were scheduled Monday on the victims and their names would be released later, the King County medical examiner's office said.