To me, it seemed like the cops were worried there might be someone else in the hotel room. They had had reports of a rifle being out a window but no one came out of the room with a rifle. I could be wrong, but it seemed like this might have been the reason they didn't approach him while he was lying down. They did ask more than once if there was anyone else in the room.
Maybe the other cops were so worried, but the cop who shot Shaver is a psychopath. There was no fear in his voice as he tormented Shaver. This is just indefensible.