What was happening ...?
Use the past continuous to express what was occurring at a precise moment in the past. The past continuous is often used together with the simple past to express an interrupted action. The action which was interrupted is expressed using the past continuous, while the action which caused the interruption takes the past simple.
Subject + to be + verb + ing + objectsThe bank clearance was being issued when everything was put on hold.
Subject + to be + not + verb + ing + objectsThe bank account wasn't being investigated when a client came in.
Wh? + to be + subject + verb + ing?Was he visiting his local bank branch when the manager offered him a job?
The actual yield was rising when the central bank acted.
Examples of What Was Happening ...
Joan was reading her account statement last Tuesday when her broker called.
Were you checking your bank balance when you got the notice your checking account was overdrawn?
The bank account wasn't being investigated when a client came in.