I will give individual cops the benefit of the doubt. Here are the things I fault this guy for:
1. Shooting a dog that is 'running at you and barking'. That is pretty much all the info we have on the dog's behavior, and if that's ALL the dog was doing, sorry but no, not enough justification to shoot the dog, IMHO. Just about every dog in the universe will run at you and bark in their yard. If it runs at you and snarls and JUMPS at you or something, shooting it might make sense. If it bites your leg, shooting it makes sense. A dog running up to you and barking because you - guess what - waltzed into its yard in a manner that probably resembles stalking (given the fact that you've stupidly withdrawn your firearm) is no reason to shoot it.
I know some will disagree with me here and say that a dog running up to you in a 'threatening' manner is enough justification to shoot it. We will have to agree to disagree on that point, because I don't think a dog barking at you and running up to you in its own yard is unusual enough behavior to be considered threatening.
2. Having his gun drawn in the first place, which we've already gone over and seems to be more or less universally acknowledged as a poor decision.
Now, as for my thoughts about the guy:
1. I think he made bad decisions and deserves consequences up to and including the loss of his job, but I certainly don't think he deserves to be called 'bloodthirsty' or whatnot. Trigger-happy, yes, probably, but that's not the same thing. I would consider him a bad policeman if for no other reason than that in my judgment he reacted poorly under a very MINIMAL degree of pressure, but not a bad person.
2. I would not want this guy in my neighborhood, armed, because clearly he lacks the decision-making skills to differentiate which situations are and aren't appropriate for having your gun drawn and ready.