Hugh Hefner's death rang through the country last week as people realized another American legend left the world.
Now, E! News has learned the cause of the Playboy mogul's death. According to his death certificate, the 91-year-old passed away after going into cardiac arrest and suffering from respiratory failure.
The certificate also notes that Hefner suffered from a recent bout of E. coli and Septicemia (a severe blood infection), listing them as contributing factors to his declining health and eventual passing. We've learned the E. coli was highly resistant to antibiotics.