If you want to know how police think, then you should read books marketed towards police. One book I just ordered, Deadly Force Encounters: What Cops Need To Know To Mentally And Physically Prepare For And Survive A Gunfight (here), says this about police shootings:
In a cop's world it's kill or be killed, but the truth of the matter is that a shooting's aftermath is often the most dangerous time for the cop. This unique life- and career-saving manual contains every shred of critical information the police officer needs to survive the media, investigations and more.
How 'bout that?
To be fair, the book is not about how to cover up a crime. It's a book on fear. (Indeed, I bought the book after seeing it referenced in the very interesting, Extreme Fear: The Science of Your Mind in Danger) (here).
It's also a book on trauma. Many officers suffer post-traumatic stress disorder after killing a suspect. Most police are not trained killers. Most officers suffer psychological problems after killing someone. Those who view cops who shoot suspects as "evil" would be advised to read the book.
However, the police attitude, post-shooting, is not about facilitating the truth. It is about protecting the cop who shot the suspect. Judges, lawyers, and jurors should remember that when deciding whether to credit police testimony. In at least a generalized sense, police do view investigations into police shootings as Us-And-Them.