Neither am I, but it's a long way from the dispassionate and clinical treatment of an injury in your surgery, to watching a much loved pet shot to death before your very eyes. I guess we're all a little surprised that you would put the shooter first, in that circumstance.
This officer was told to apprehend a possible drug dealer (report of money flying out of the car.) He had a job to do. He didn't chose to apprehend the car on a whim; he was ordered to the scene.
Perhaps your situation is different, but in California officers are sued for everything under the sun and expected to have the wisdom of Solomon in tricky situations where their lives are on the line if they judge wrong.
I always give policemen the benefit of the doubt in close calls, as I know that no one can perform a perfect job under all circumstances, especially when they have to make an instant decision with limited information.
I am here to say that a human being is worth more than a dog, even a beloved family pet. And if there is a doubt in a situation where a human may be injured, perhaps seriously, I will never blame someone for chosing on the side of self defense.