He bought two tickets from a 7 Eleven store he passed regularly on his way home. They cost him $60. One of them turned out to be the million-dollar jackpot.
After taxes, the winnings for Mr Khan, who immigrated to the US in 1989 from Hyderabad, amounted to about $425,000 (Rs. 2.30 crore approximately). The check was issued about a month later, on July 19.
The next day, Mr Khan was dead. He was rushed to hospital after he woke up screaming in the middle of the night; doctors declared him dead on arrival. They said he had died of natural causes.
However, an anonymous call to the police provoked a deeper investigation which revealed that Mr Khan was poisoned with a lethal amount of cyanide.
"I don't think anyone would have a bad eye for him or that he had any enemy," said his wife, Shabana Ansari, adding that she continues to work at the dry cleaner out of a desire to honour her husband and the businesses he built. She said he planned to use the lottery winnings to pay off mortgages, expand his business and give a donation to the St Jude Children's Research Hospital. Ms Ansari said her husband did not have a will and the money is now tied up in probate.
Authorities are now investigating Mr Khan's death as a homicide. While they do not have any suspects and a motive has not been determined yet, the police haven't ruled out that Mr Khan was killed because of his big lottery win. Authorities plan to exhume Mr Khan's body in the next few weeks in hopes they might be able to test additional tissue samples and bolster evidence if the case goes to trial.
"It's always good if and when the case goes to trial to have as much data as possible," said Cook County Medical Examiner Stephen Cina. He added that he did not believe additional testing would change the conclusion that Mr Khan was a homicide victim, saying those comprehensive toxicology results were validated in the lab.
Mr Khan had recently fulfilled a long planned pilgrimage to Mecca. According to reports, his family said he had decided not to gamble in any manner after returning from the hajj.