Simplify the following text for a Grade 5 native English-speaking person.
Original: In 1662 , at the age of 39 , Koxinga died of malaria , although speculations said that he died in a sudden fit of madness upon hearing that his father was executed by the Qing government in Beijing .
Simplified: In 1662 , at the age of 39 , Koxinga died of malaria . Some people said that he died in a sudden fit of craziness when he heard about the death of his father under the Qing .