There is really insufficient information given to determine whether a SAR should be filed. Is this a long-time customer? Is it a business or personal account? How much is a large sum of money? Who were the payees on the cashier's checks that he/she returned? Why were these checks returned? Who are the beneficiaries of the wire transfers? Where are the wire transfers going to? How many unusual transactions has this customer had? What time period is meant by "watching for a while?"
What it comes down to is your knowledge of the customer (KYC,EDD,CIP). You have been watching this customer for some time, but what was it that triggered your investigation?
It's really your decision, but make sure that you include all the facts available before you file a SAR. (Also, make sure you describe this in your SAR.)