Killing That Guy Who Might Deserve It

If a guy tells you there is a 5% chance he might kill you someday in the future, do you have a moral justification to kill him today?

My answer is yes. You would have a big legal problem, but from a moral standpoint, it's close enough to self defense in my book.

But what if the guy is a bit hard to read on the subject of whether he might kill you in the future. Let's say you can't estimate the odds of it happening because you're not even sure if he means it, or maybe he has some motive in making