I can only speak from my experience and training. I was a Deputy sheriff in KY. Under KY law you do not have to wait until you are attacked to begin to defend yourself . You are allowed to use force in a preemptive manner if a "reasonable person" would fear an eminent attack was about to be launched against you. If a reasonable person believed the attack was going to be of a nonlethal nature , "deadly force " would be inappropriate.. This would be when the use of nonlethal force would be justifiable but lethal force would not be justifiable.
Mitigating factors might affect the situation. Are you outnumbered or grossly out sized? Are you disabled? Are you trained in the use and retention of weapons? One person might be believed by a grand jury to be " reasonable " , wherein another in the same circumstance might not be thought to be "reasonable".
For instance, I am a former Law Enforcement Officer with a great deal of training and experience. I am likely to be held to a higher expectation, to use a lesser means of force, than an untrained person in the same situation.
I am basing my opinion on the law as it stands in our present situation and not in a situation where a total breakdown of society and law has occurred. Such a situation would undoubtedly be a mitigating factor in the mind of a grand juror.
In short , justification for the use of force being reasonable or unreasonable is always left to the judgment of a Grand Juror, with the exception of a limited number of circumstances narrowly defined by the “Castel Doctrine”.