What could have caused Brittany Murphy’s death?

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Brittany Murphy at the "Happy Feet" Sydney Premiere at Fox Studios in Sydney, NSW. (Photo by Dani Abramowicz/FilmMagic)

The sudden death of 32-year-old actress Brittany Murphy from a reported cardiac arrest on Sunday morning has left her friends and loved ones scrambling for answers, and the public wondering what could have ended the former Clueless star’s life so abruptly. Initial reports suggests that Murphy died of natural causes, and an autopsy, which will include tests for drugs and alcohol, is currently being conducted. To learn more about what could possibly have caused sudden cardiac arrest in the young actress, TIME spoke with Dr. Douglas Zipes, former president of the American College of Cardiology.