Complex sentence: A contributing reason for the reaction was the mysterious circumstances in which the fit 33-year old had died, reportedly from a heart attack in the middle of the night, and calls have been made for a police investigation into his death.
Split into simpler sentences: A contributing reason for the public reaction was the mysterious circumstances in which the fit 33-year old had died, reportedly from a heart attack in the middle of the night. Calls have been made for a police investigation into his death.