I can't help noticing that you've switched a homicide victim with a murder defendant. A more appropriate analogy might be of a Joe Arpaio fan allegedly being murdered by someone who happened to be Latino, who then claimed self-defense.
I get that you're trying to pose the question of whether the homicide victim was also an aggressor, but if so we need to include the context that the person in question was fleeing the defendant when the alleged aggression took place.
If I chase you down the street for no good reason, and you turn around and punch me in the nose, who's at fault?
If you just chase, not brandishing a weapon, screaming threats or in some other way giving a person being chased reasonable fear for his life, then the person punching is at fault. Running on the street is not a violation of anybody's rights, and you do not have to have any specific "good reason" to run on the street, neither is running while other person is present on the same street. Punching one in the nose, on the other hand, is.
I get that you're trying to pose the question of whether the homicide victim was also an aggressor, but if so we need to include the context that the person in question was fleeing the defendant when the alleged aggression took place.
If I chase you down the street for no good reason, and you turn around and punch me in the nose, who's at fault?