The Fairwood couple found dead in their Fairwood home March 9 were strangled to death, the King County medical examiner announced Thursday.

The deaths of Robert R. Taylor, 82, and Norma J. Taylor, 80, were ruled a homicide by ligature strangulation by the medical examiner.

The Taylors’ grandson, Michael “Chadd” Boysen, 26, is the prime suspect in their deaths. He’s being treated at the Legacy Emanuel Hospital in Portland for what appear to be self-inflicted cuts suffered in a standoff with police Tuesday in Lincoln City, Ore.

King County Prosecuting Attorney Dan Satterberg will not decide Thursday about charges against  Boysen, said Dan Donohoe, his spokesman.

The Prosecuting Attorney’s Office will begin the extradition process to bring Boysen to King County once charges have been filed, Donohoe said.

The state Department of Corrections also can extradite Boysen for violating the terms of his release from the state prison in Monroe on March 8.