Hemet is right, if it had been a small dog, it probably would not have been shot, but because this was a large black dog, it is likely that the police officer associated it more negatively and therefore interpreted it's actions as more dangerous. This is a common phenomenon known as "big black dog" syndrome, and it is the reason why large black dogs are the least likely to be adopted from animal shelters. I used to own a large black mastiff and people would cross the street to avoid having to pass me and my dog on the sidewalk. Eventually I resorted to dressing her in festive leashes and collars, scarves and painting her toenails to match because I was concerned for her safety, as people had fearful, negative and even hostile attitudes towards her, pretty much just in reaction to her appearance. My point is, whether they realize it or not, the cops probably overreacted because they situation was heightened and large black dogs carry more psychological associations that are negative. Another example if that is snakes, people are often terrified of snakes, even though in reality they are unlikely to be harmed by one. Even knowing that intellectually, many people will still kill every snake they see, even helpful garden snakes because they have such a negative belief/association for snakes. So basically you have a situation that "loaded the gun" so to speak, and then you have certain attitudes and prejudices which created the response.
