Wash. Rev. Code § 9.46.212
When physical injury to a person or substantial damage to property occurs, or is about to occur, within the presence of an officer of the commission designated with police powers pursuant to RCW 9.46.210, the designated officer is authorized to take such action as is reasonably necessary to prevent physical injury to a person or substantial damage to property or prevent further injury to a person or further substantial damage to property. A designated officer shall be immune from civil liability for damages arising out of the action of the designated officer to prevent physical injury to a person or substantial damage to property or prevent further injury to a person or further substantial damage to property, unless it is shown that the designated officer acted with gross negligence or bad faith.
RCW 9.46.212