To be fair, he already implied he won't be taken alive. Rules of engaging anyone with lethal force is; if your life is in danger, you end the danger. Just being in a clear line of sight of this guy puts you in danger (that is, if you're a police officer).
To be fair to the suspect, he already knows he won't get a fair trial, especially since the trials he did have weren't fair, according to him.
This whole situation is terrible. I don't agree with this man's actions, but I also don't agree with the LAPD and their actions. I also think it's unfair how this guy is being painted.. I saw CNN had an interview with a criminal profiler, and he basically said the guy was a psychopath. The manifesto itself shows he isn't by definition a psychopath, not to mention people who know him. Yet, the media does this with the support of the LAPD to try and make this as black and white as possible.