Washington Revised Code Title 11. Probate and Trust Law § 11.12.040. Revocation of will--How effected--Effect on codicils

(a) By a subsequent will that revokes, or partially revokes, the prior will expressly or by inconsistency; or

(b) By being burnt, torn, canceled, obliterated, destroyed, or a physical act, with the intent and for the purpose of revoking the same, by the testator or by another person in the presence and by the direction of the testator. If such act is done by any person other than the testator, the direction of the testator and the facts of such injury or destruction must be proved by two witnesses.