Batgirl #24 pg 16

From the Bruce Wayne: Murderer arc, issue 24 finds Oracle sending Batgirl to Wayne Manor to investigate the crime scene... while the cops are there.

In the process she wanders the mansion and is privy to this exchange between two GCPD detectives talking about the Wayne murders. Grabbed this page with the one that follows because it sets the stage for Cassandra figuring out that Bruce Wayne and Batman are the same person later in the issue.