The moment he opened it, he was dead even before reading it. It was a shock to the entire nation why and how he died by just opening a letter. The letter had no bomb planted, no cyanide and no shocking news which could have given him a heart failure . Investigators were almost exasperated seeing the situation in which the body was found – with no clues and no such mystery of occult science involved.
The day they opened the open letter, things surface clearly dissolving the other possibilities – it was the laugh, he died seeing a blank letter being send to him with a warning – DO NOT OPEN IT, IT WILL COST YOU YOUR LIFE.