A reasonable fear of severe injury or death that justifies the use of deadly force can exist by circumstances that are not completely the fault of the person who has been killed.
He chased Kyle (his fault)
He threw something at Kyle (his fault)
Someone nearby fired a gun making Kyle think it came from the guy behind him (not his fault).
It is also reasonable to assume the guy chasing him had a gun, because who would be so stupid as to chase someone with a firearm without one.
Chasing someone is an act of aggression. Chasing someone that you know is carrying a firearm is just plain stupid. If you do that, and some unfortunate coincidence like this occurs at that time, you may justifiably be shot.
Yep, and I think any reasonable person would agree with that.