How did Mao die? And why would he kill members of his communist party?
You are obviously young. Mao was getting on in years. Although, a book by his doctor alluded to other reasons for his death.
The Communist party is like any power-hungry organization, just much more ruthless. He had anyone seen as a threat assassinated. Also, dead men tell no tales; as he got older, the stories of his exploits during the Long March got more exaggerated. He killed many of those who might contradict those new stories of Mao’s past exploits. Read Machiavelli’s The Prince.