The officer acted as he felt he needed to. Some people don't agree with it, some do. If you dive deeper you can find worse cases than this all over the place (like listed above). What people are not saying is that there are millions of officers that do make the right decisions everyday. In normal lines of work a mistake means someone gets mustard on a plain burger or some customers bill may be high. When officers make mistakes people can die... it's part of the job. When you are in a situation that's escalating you are going to have to make a fast decision. They felt his decision was the right one.
For those looking for fault in our police force think about this. It's like I tell my employees at work... When you look that closely at anyone, no one looks good. If you go searching for instances of where police are being dicks and abusing their power you will find many videos and even more documented reports. The same way that if you look through my thousands of videos you might find some fat girl on giraffe porn. It doesn't mean all I watch is fat girl on giraffe porn. I think that's the problem now is people are searching for stuff to make it seem like all cops are bad to justify how they feel. It's not making anything better.