Instagram/Nicholas Brendon TV Buffy star Nicholas Brendon's cause of death revealed: atherosclerotic and hypertensive cardiovascular disease, with contributing factors, ruled natural. May 5, 2026 AceShowbiz - The cause of death for Nicholas Brendon, known for his role in Buffy the Vampire Slayer, has been officially disclosed following his passing on March 20 at age 54. The Putnam County Coroner's office confirmed on Wednesday that Brendon died from atherosclerotic and hypertensive cardiovascular disease.