In case you do not already have them here are some numbers to call who WILL make sure the Sheriff Dept do their job.
CARE Crisis Line: 800-584-3578 or 425-258-4357
Eastside Domestic Violence Program: 1-800-827-8840
National Domestic Violence Hotline: 1-800-799-SAFE (1-800-799-7233)
Providence Sexual Assault Center: 425-252-4800
Snohomish County Center for Battered Women: 425-25-ABUSE (425-252-2873)
Washington State Domestic Violence Hotline: 800-562-6025

Also calling in the State Troopers may get you a more responsible path from Law enforcement Officers.
If a Passport and a Social Security Card are among the personal items missing, please report this to the State Police who will then contact the FBI.
As there is an order (App.in 50 states) against this Bastard, legally issued in Maine, your Mother should be given protection by an Officer when collecting HER belongings at the abuser's home no matter what State that residence is in.
I suggest you try ALL these routes Tami.
Safety first and above all remember that this is only one man who is a weak SOB and the Law is on your Mother's side.
With you both in spirit.