Un-natural Causes?

In an SCMP story on the death of Vice-premier Huang Ju (from pancreatic cancer), Josephine Ma writes:

“Yuan Weishi , a Guangdong-based historian, said although the party could appoint a replacement for Huang on the Politburo Standing Committee, this was unlikely to happen so soon before the congress. Professor Yuan also believes Huang is one of only a few members of the party’s top echelon to die of natural causes in office.”

What??? Am I missing something here? Is something else – something unnatural – killing top party leaders?