He was just days from receiving his winnings when he died before dawn on July 20.
The night before, Khan ate dinner with his wife, daughter and father-in-law in their house in Chicago's North Side neighborhood of West Rogers Park, home to many immigrants from India and Pakistan.
Sometime that night, Khan awoke feeling ill and collapsed as he tried to get up from a chair, his wife has said, according to the Chicago Sun-Times.
With no outward sign of trauma, authorities initially determined Khan had died of natural causes. But a concerned relative — whose identity remains a mystery — came forward with suspicions and asked authorities to take a closer look.
Further toxicology tests found a lethal amount of cyanide in his blood, leading the medical examiner in November to reclassify the death a homicide.
Khan died without a will, opening the door to a court battle. The businessman's widow and siblings fought for months over his estate, including the lottery check.