For one thing, the traumatic events seem to have begun because the dog's owner was using his cell phone to engage in his very legitimate right to photograph cops in public in performance of their duties, in case any police brutality went down and needed to be documented. The DOJ has recently made clear that such conduct is not only legal but also is an important part of legitimate government oversight. As is clear from the video, the man was not interfering in any way with police activity, but rather was using his cell phone to record events from a distance and to the extent it occurred to engage in photographing brutality.
Well, police brutality did occur that day, only the man attempting to document it turned out to be the victim. Thankfully, other citizen journalists were also doing the same thing, exercising their right to engage in photographing brutality, and because of it he now has the evidence he will need to get justice for what happened to him and to his Rottweiler dog who was brutally and needlessly shot and killed by cops in Hawthorne, California.
For another thing, after the cops precipitated hostilities by cuffing the man, apparently simply for exercising his rights, they shot and kill his Rottweiler, who escaped from the car in order to assist his owner. From the video, it seems that the dog was basically under control at the time of the shooting and was milling around the area but was being kept at bay by his owner's commands.
The cops could have eschewed force altogether -- releasing the man and letting him handle his dog -- but in any event could have and should have used any other less-lethal options at their disposal. Considering the video shows a swarm of cop cars, it stands to reason there were plenty of less-lethal weapons at the scene. At least there should have been.
Shooting and killing someone's dog is not only extremely hurtful and destructive, but if done without proper justification it is a violation of the Fourth Amendment right against unreasonable seizure, as was made clear in the Ninth Circuit case of San Jose Charter of Hell's Angles Motorcycle Club v. City of San Jose.
Finally, the fact that the dog's owner was out monitoring the cops and potentially engaging in photographing brutality, and the commentary on the video that the people filming didn't want to "get shot," just goes to show the level of fear and distrust that cops and their excessive force tactics are engendering in certain Los Angeles neighborhoods.