The password of victim's locker is "ACE".
The password of locker of victim's mother is "1614".
The password of piano is "CCCBCdEdC" (C, #, C, #, C, #, B, C, #, D , E , D, C, #).
At the end of the investigation, you need to choose the right letters on the keyboard sent from the crime lad. There are 12 letters each stacked 3 high:
First line ... second H, third Y, third Q, first A, first S, third J.
Second line first F, second R, first E, second T, second C, third O.