Michael Madsen, the actor best known for his coolly menacing, steely-eyed, often sadistic characters in the films of Quentin Tarantino including “Reservoir Dogs” and “Kill Bill: Vol. 2,” has died.

Mr. Madsen was found unresponsive in his home in Malibu, Calif., on Thursday morning and pronounced dead, Los Angeles County Sheriff's Department Watch Commander Christopher Jauregui said. He is believed to have died of natural causes and authorities do not suspect any foul play was involved. Mr. Madsen's manager Ron Smith said cardiac arrest was the apparent cause. He was 67.

Mr. Madsen’s career spanned more than 300 credits stretching back to the early 1980s, many in low-budget and independent films. He often played low-level thugs, gangsters and shady cops in small roles. Mr. Tarantino would use that identity, but make him a main character.

His torture of a captured police officer in Mr. Tarantino's 1992 directorial debut “Reservoir Dogs,” in which Mr. Madsen's black-suited bank robber Vic “Mr. Blonde” Vega severs the man's ear while dancing to Stealers Wheel’s "Stuck in the Middle with You” was an early career-defining moment for both director and actor.

He would become a Tarantino regular. He had a small role as the cowboy-hatted desert dweller Budd, a member of the Deadly Viper Assassination Squad, in 2003's “Kill Bill: Vol. 1," then a starring role the following year in the sequel, in which he battles with Uma Thurman's protagonist The Bride and buries her alive.