Detectives in Chicago are investigating the mysterious death of a lottery winner killed by cyanide poisoning.

Urooj Khan, 46, won a $1,000,000 lotto prize last summer after spending $60 on two scratch-off tickets from a 7-11 convenience store near his home in the West Rogers Park neighborhood. He was dead just days later on July 20, a victim of what doctors initially blamed on hardened arteries. They were so confident that an autopsy wasn’t done.

The Khan family wasn’t quite so convinced, though, and quietly asked investigators to take a second look. Now the Chicago Tribune is reporting the cause of death has been changed from natural causes to homicide after a medical examiner found a lethal amount of cyanide in Khan’s system.

His family told detectives Khan had planned to invest some of his winnings into the dry cleaning business he owned but never got the chance to see the check for $425,000 that was issued on July 19. Khan’s wife, Shabana Ansari who described him as “the best husband on the planet,” said he woke up in the middle of the night screaming before being taken to the hospital.

"By God's grace, he was a workaholic," Ansari said. "Day or night ... he picks up the phone 24/7. He made the clients happy by doing his job. He could not be everywhere, but he had to be everywhere."

Police refused to speculate on a motive but would not rule out the obvious idea that the lottery winnings may have made Khan a tempting target. Cook County Medical Examiner Stephen J. Cina told the Chicago Sun-Times the case was only getting started. The next step could be exhuming the body.

“That seems to be the way things are heading,” Cina said. “Depending on the condition of the body, we may be able to document the extent of any pre-existing conditions and do additional toxicological testing on other specimens. … At the time, there was no suspicion of foul play based on the history provided.”

Last month a Florida woman was sentenced to life without parole after being convicted of the first-degree murder of Florida Lottery winner Abraham Shakespeare, who won millions of dollars in 2006.