Steve Chaisson and Dmitry Tertyshny were killed a couple months apart in 1999, and Stephane Morin died midway through the previous season, so yes it has happened.
In 1986 the Pelle Lindbergh crash, Swift Current bus flip, George Pelawa (Calgary 1986 #1 pick) death, and the death Anatoly Fetisov (Slava Fetisov's younger brother, projected to be a star) all happened inside a year of each other.
It is intriguing how accidents and tragedies often occur in bunches in such a short timeframe (e.g. the deaths of Bourdon, Renaud and Cherepanov).
Slightly off topic, but this reminds me of how the Zednik accident last season was followed within days by two other skate-related incidents (relatively minor, thank Heavens) around the league, and how this sort of thing seemingly never occurred before that week.