This is so tragic. R.I.P.
Kunzite seems to be an unlucky character as far as deaths go. His seiyuu from the original anime, Kazuyuki Sogabe, passed away in 2006 from esophageal cancer at age 58, and his DiC English voice actor, Denis Akiyama, passed away in 2018 from cancer at age 66. His original French voice actor (Francois Leccia) also died in 2009 at age 60.