So your claim that he was executed is ludicrous. Someone who is executed generally does not have the ability to fire back.
“...... He was not disarmed, and continued to fire at officers.”
That is just not true DB. Dorner had not fired at officers from the house in over an hour. They could not even find him in the house,so how was he shooting up until the end? That part of your facts are not in evidence at this point.
Substitute "killed without a court decree" then. One justification for use of deadly force is that your own life is at imminent risk (more technically, that there is reasonable fear of imminent serious injury or death).
The case that you cited was that deadly force can be used to prevent escape. My contention is that resort to arson was had, in order to kill Dorner. The police deny both. They deny an intention to set fire to the structure, and they deny an intention to kill Dorner. Neither of those denials is credible. However, you are arguing that both of those action are legal and justified. IOW, there is more than one argument going on here. Not even the police are adopting your point of view.