This whole thread is irrelevant. Who requires a goy to follow Torah law? Who says that the din of rodef applies to a goy? And what precisely is the issur to kill a goy? I learned that killing a goy is not murder. It’s bal tashchis. So why are we investigating rodef?
It’s a common problem in the CR that we seek to apply halacha to goyim. Outside of Sheva Mitzvos, they have no allegiance whatsoever to Torah Law. If these discussions were academically interesting, that might justify them. But they are simply foolish. I would have hoped the OP would have hypothesized that the players were Jews (chas veshalom) and inquired about the halacha then.
Goyim have no issur of mesira or arkaos, and they do not need their courts to apply the same restrictions to witnesses as halacha requires of beis din. But we hear such arguments here.