After the initial shock of the sudden death of Michael Jackson, speculation is turning to what claimed the life of the King of Pop.The 50-year-old was rushed to hospital from his home suffering a major heart attack. Some reports say he was unconscious and not breathing by the time he arrived at a Los Angeles medical centre. The death came just weeks before a series of long-awaited come-back concerts. A family lawyer today said he had been concerned that Jackson’s use of prescription drugs for dancing-related injuries would one day prove fatal. Brian Oxman said the entertainer’s inner circle had ignored his warnings. An autopsy is due to be carried out, but authorities say it could take weeks to determine the cause of death. Toxicology tests will ascertain whether Jackson had any drugs, alcohol or prescription medication in his system. There has been an outpouring of grief among the fans of this former child star who became one of the best-selling pop artists of all time. His death has been the top headline in the media, right across the globe.