"Oh, it's been very effective," Daley said, according to MyFoxChicago.com. "If I put this up your butt, you'll find out how effective it is. If I put a round up your … you'll know."
Daley, whose comments came at a news conference on Thursday previously scheduled to discuss the city's ban and a pending U.S. Supreme Court lawsuit challenging the law, became testy when a reporter questioned the ban's effectiveness as the mayor held a rifle confiscated from city streets.
Jacquelyn Heard, Daley's press secretary, later told the Chicago Sun-Times that Daley was somewhat exasperated because the individual asking the question -- a reporter from the Chicago Reader -- was "missing the point that unrestricted guns are a devastating issue" for the city.
"To illustrate the point, he offered what admittedly could be considered a less than ideal example, but it's one that is a stark reminder of how destructive gun violence has been," Heard told the paper.
Thomas Wortham IV, a 30-year-old Chicago police officer who recently returned from a tour of duty in Iraq, was shot and killed Thursday when several people approached him outside his family's home and tried to steal his new motorcycle, authorities said.
Wortham IV's father -- a retired Chicago police officer -- came to his son's aid and shot two of the attackers, killing one of them late Wednesday, police said. Retired police officers are allowed to keep guns.
"This is a tragedy," said Chicago Alderman Freddrenna Lyle. "This young man survived two tours in Iraq, and came home and got murdered on the streets in front of his house that he grew up in. In front of his father, it's just unbelievable."
The Associated Press contributed to this report.