Mao Zedong
At around 5:00PM on 2 September 1976, Mao suffered a heart attack, far more severe than his previous two and affecting a much larger area of his heart.  Three days later, on 5 September, Mao's condition was still critical.  On the afternoon of 7 September, Mao's condition completely deteriorated.  Mao's organs failed quickly and he fell into a coma shortly before noon where he was put on life support machines.  He was taken off life support over 12 hours later, quarter to midnight and was pronounced dead at 12:08 am on 9 September 1976.