Well, unless you can think of a reason why someone would want to kill David Carr for interviewing Snowden, Greenwald, and Poitras, but not be motivated (or not able) to kill Snowden, Greenwald, or Poitras themselves, the answer is probably 'yes.'
I don't seriously think that Carr was assassinated, but Andrei Sakharov (Soviet scientist, human rights activist) believed that the KGB killed people near him because he personally was too high-profile to be killed without international outrage.
Yeah, Snowden and Greenwald have insurance policies. Carr likely didn't. If they kill Snowden or Greenwald, more secrets leak. Why do you think Snowden's been so slow to release everything?