It's only self-defense if the threat is legitimate and not already neutralized. Even if a murderer has expressed their intent to escape and kill again, if they are already captured and constrained executing them is wrong.
Some deaths in the process of neutralizing threats may be unavoidable and just. That could include resistance or revolution. But, no, you don't get to justly kill anyone based on their mere willingness to kill you.
I certainly think it is possible to argue neither of those threats were/are neutralized. But that may say more about me than I really want to impose on anyone else.
"No War But Class War" ?