Oh I don't think they'd overtly kill him. Torture, imprison, exile, leave him marooned, break him economically, sure, any of those things, and I'm sure they have black bag people to 'accidentally' take care of him if needed.
At this point you have to remember that there are only two criteria: A) He can't ever be allowed to look like he 'won', like Ellsberg did and B) it has to be public, so that anyone else considering an ethical stand will know that their life is irrevocably ruined if they do.
At this point you have to remember that there are only two criteria: A) He can't ever be allowed to look like he 'won', like Ellsberg did and B) it has to be public, so that anyone else considering an ethical stand will know that their life is irrevocably ruined if they do.