In the exceptional and absolutely must be seen documentary, The Black Panthers: Vanguard of the Revolution, there is a witness who is describing the Chicago Police's assassination of Fred Hampton, and she says (I am paraphrasing) that the police had made a terrible mistake by not locking the flat up, and sealing the "crime scene".
I am here to tell you there was no mistake made. The Chicago Police and Hoover and the FBI left that house open on purpose. They were sending a message to all the black folks and Black Panthers, in Chicago, and throughout the country and the world: "This is what we do," they said, "To uppity negroes."
Everyone, please take a couple of hours out of your busy lives, and watch Stanley Nelson's timely and important documentary. You will be better for it.