The cops are mystified. They’ve been bamboozled. A bunch of head-scratchers. And yet, they know exactly why and how this happened.
They just can’t state what they think happened lest they throw the case into disarray. Their statements of uncertainty is meant to protect the case from being thrown out. They also keep cards close until they have all the fact and all accused associated with the crime lest there are others and they tip off those involved but not yet arrested.