Yes, we recommend contacting your local law enforcement regarding the forgeries, particularly if you may have information that could assist police in identifying the fraudster.
In addition, we are not aware of any form requirements regarding affidavits of forgery for checks, although you should check for any clearinghouse rules that might require an affidavit or other form when returning a forged check. In the absence of a form requirement, we believe you may use either the county of your main bank or the county of the two branches where the forged checks were presented, whichever creates the most useful record for your bank. However, we note that the various sample affidavits of forgery we found online typically include the state and county where the customer resides or where the affidavit is notarized (or both) — not where the bank is located.