Dude, you need to chill out. Everything everyone says here is just an opinion.
Regarding "ends justify the means." sometimes protests are a useful tool to bring about change and sometimes deadly force is required when the police are making an arrest. In my opinion, deadly force certainly wasn't justified in the Dubose situation.
Regarding the cause of the shooting, there was just one cause: Tensing. Every other cop in America opts not to shoot Dubose in the head. Tensing's actions were not reasonable.