Opening Someone Else's Financial Documents

My question involves criminal law for the state of: New York

In the past 3 months my sister started to steal the identities of members of our family. We all live in the same house. We are all of age. She wrote checks, sent herself money western union and even took out a cell phone using bank statements and other financial paperwork and stolen credit cards. They haven't gone to the cops yet. A couple days ago, after I caught her stealing cash out of a purse, I woke to two flat tires. The next day, soda poured on car. The day after, soda in the gas tank. Installed a camera and had one night of peace. Yesterday, my tax documents and 401k information was found sitting on her bed. All letters that were never delivered to me. All of my personal information and accounts. Obviously I cant prove the car problems yet, but mother and grandparents were the ones to find my opened mail sitting in her bedroom. How can I protect myself? Who do I turn to and what can even be done?

Short of moving out, your best bet would be to switch everything to a post office box that only you control.
Pull your credit report and look for unusual things.
If she's gone beyond OPENING the mail, report these things to the police and the credit cards or banks involved.
You may wish to close any compromised accounts. Most credit cards and many banks have no problem reissuing things under new numbers in identity theft situations.

You can also subscribe to one of the three credit reporting companies like Equifax and put a fraud alert on your credit report. From that point on you will have to be contacted before any new credit accounts or loans can be opened.

Thank you all for the help