Much depends on the circumstance, and the circumstances would have to be mighty unusual to justify this action. I have a pretty strong feeling that in this case "just shooting a cop" was not justified.
A 19 year old with two felony convictions wanted for a burglary.
That pretty well addressed the “circumstances,” does it not?
In addition, the woman in question didn’t care about the “circumstances.” Perp shot a cop. That’s all she needed to know. That’s Ok with her.