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One Mile is a Little big for the effect and most Settings would have the Problem that no character is going to transform back anytime soon. It would probably be more interesting if anyone who does this makes it into a more local effect, like 150 metres and line of sight. Otherwise, unless you are Ryoga from Ranma 1/2, you are unlikely to transform back anytime soon.
So someone 150.1 meters behind could shoot the person and the charm wouldn’t be able to do anything about it.
The Charm does include something along the line of making sure that the Person doesn't notice the effect. And most series don't have villains that would snipe the Hero now that I think about it. Except that case I heard about Dresden Files.
Still, it is a divinely blessed Charm. It is not that hard to consider the possibly of secondary protection. The soldier in Vietnam could have easily ended up dead due to artillery fire or bombings without the one Shooting even knowing that he even exists.
After all, you cannot feel agression or other negative emotions about someone if you don't even know they are here.