The situation where large numbers of bank customers simultaneously withdraw funds from their bank account is called a run on the bank or bank run. It is inevitable that during such an event, the bank ends up with liquidity problems. These liquidity problems result in a bankruptcy of the bank. Therefore central banks have to respond adequate in order to prevent these difficulties in the financial system.
Fortunately bank runs are anticipated quickly and a soft landing is offered by either by enabling capital controls or the activation of a deposit guarantee scheme.