Celebrity death hoaxes can be started surprising easily.
Basically, all you have to do is start a "RIP (CELEBRITY)" Facebook page, and the Internet will do the rest. If you're lucky, a publication will falsely report on it (as is this case with Variety and Terry Gilliam), and it'll turn into an even bigger hoax. Here are a bunch of examples of other times it has happened.
1. Paul McCartney
The original celebrity death hoax, "Paul is Dead" even has its own Wikipedia page. It involves fake car crash reports, secret messages hidden in album art, and Beatles songs with hidden messages that can only be uncovered if you play them backwards. Yep, other hoaxes can only dream to achieve "Paul is Dead" status.