Ozzy Osbourne's cause of death has been revealed. According to a death certificate viewed by the New York Times and The Sun on Tuesday, the Black Sabbath star died on July 22 due to "out of hospital cardiac arrest" and "acute myocardial infarction," AKA a heart attack. Coronary artery disease and Parkinson's disease with autonomic dysfunction were listed as "joint causes." Ozzy's daughter Aimee submitted the death certificate at a registry in London, the Times reported.