What would killing him achieve? The Bitcoin technology is out of his control.

You probably won't get killed, but of course you might by someone looking to make a point, in any case your life is gonna get turned upside down, various interests are going to want you to do things for them, people will want to hire you to say things or confer them legitimacy, people will want you to opine on things, etc.

If you're in a nice enough place to dedicate the time to a project like Bitcoin is that something you really need? If you have sufficient frame of mind to develop Bitcoin that's probably not something you want in the first place.

"Hit him with this $5 wrench until he tells us his passphrase." Which he has likely forgotten or lost.