Cause of death: heart attack
Brion Howard James (February 20, 1945 – August 7, 1999) was an American character actor. He portrayed Leon Kowalski in Blade Runner and appeared in Southern Comfort, 48 Hrs., Another 48 Hrs., Silverado, Tango & Cash, Red Heat, The Player, and The Fifth Element. James was frequently cast as an antagonist, appearing more frequently in lower-budget horror and action films and TV shows throughout the 1980s and 1990s. James appeared in more than 100 films before his death in 1999 at the age of 54.
Source : Wikipedia