meaning of 'shake loose'

Solution 1:

To "shake loose" has several slightly different meanings, but in this context 'some things shook loose' does mean something has changed, probably more information / evidence has come to light.

'moving pieces' is likening the situation to the game of chess. It means that more people are involved in the investigation than expected. The whole of A's answer could be rephrased as

A: Some more information has been found. There are more people involved than expected. There might be more victims.

I gather that B is surprised that the investigation is bigger than he expected. I guess he was discussing one particular victim / crime and A explains that that is now only part of their investigation which now covers additional crimes that have since come to light (shaken lose).