The first claim on a deceased's assets is payment of the funeral bill.
What you should have done is go to the bank with a copy of the death certificate and request them to issue a cheque payable to the undertakers for the balance of your brother's account. They would have complied.
What you have done was wrong...... but I think that you will get away with it. You committed fraud by impersonating your deceased brother. However, who has lost out here?
The person that has lost out is not the Bank, it is your brother's estate (ie you, to all intents and purposes). You would have been entitled to your brother's monies as payer of the funeral bill.
The Bank will not press charges against you...... Will your brother's estate, ie you, press charges against yourself?
Just go to the Bank and now do what you should have done in the first place and request the balance still left in the account for payment of the funeral bill, and the closure of the account.