In late November, a more detailed blood analysis came back showing "a lethal level of cyanide" and Khan's death became a murder case.

Chicago police haven't offered details, including into a possible motive, about what they call an "ongoing investigation." Talking briefly with CNN affiliate WBBM and the Tribune, Khan's widow described her husband as kind and exemplary.

Jimmy Goreel, who runs the 7-Eleven where the winning lottery ticket was sold, offered similarly glowing comments about Khan.

"I would never think that anybody ... would hurt him," Goreel told WGN. "(He was a) nice person, very hopeful and gentle (and) very hard-working."