FD cashed by father, how to find out where money was invested?

Hello sir My father died on 24th may We are two sisters mother passed in 2011 Now we do know he done a fixed deposit in a bank after selling his property Now after getting a death certificate we went to bank branch manage said he took out money from that fixed deposit through self cheque or personally now how can we find why and where he invested it or given to someone Bank says they will provide a statement but how to find where if he invested as we don't have any knowledge of it nor he discussed while he was there Any place where can we go to find out by father pan card or ids Please help us As it's a big amount he took out and we don't know about it