Terrible Supervisors

A lady Infront of me at the cashier paying for her items. The cashier took her own sweet time while this patient professional looking customer waited. Her groceries were not put into packet as they were scanned but instead shoved into the packets so haphazardly. She requested a particular bag that came with a promotional item and I was horrified that the supervisor said to the cashier infront of this customer, "The bags are right there" with irritation on her face as if the customer herself should walk to get it. The supervisor returned with the bag that she got from another till and the customer then said she had not seen the bag otherwise she would have taken it herself. I was humbled by her response while the whole time the supervisor which is an Indian lady showed her annoyed she was. We all are tired at the end of a work day but the doesn't mean we should treat people badly. Hope this supervisor is dealt with for her attitude.