Why assume all this negativity on the cops? Because the news said so? Who said they are too scared to do their jobs or assess the scenes? Their worst enemies are the press and the people who vilify them because of a bunch of articles.
There has been a lot more detail on this including more video, his weapon, the real reason for the call, what information they had on him before they got there. (Perhaps my close proximity has made these stories more available). With that information you would see that comments like not knowing their surroundings etc make no sense.