His comments came as he and other officers displayed recently seized firearms.
On Friday, the Illinois legislature approved a measure that would require Illinois residents to receive 16 hours of training before getting a permit to carry a concealed gun. McCarthy says that's not enough.
"Police officers go through six months in the police academy, four months of field training, ongoing training and practicing. We make mistakes frequently," he said.
The concealed carry legislation now goes to governor Pat Quinn. But he has not indicated whether he will sign it.
The gun law passed Friday would prohibit the possession of guns in such places as schools, taverns and parks, but would allow a gun to be kept securely in a car. It did not include an earlier proposal to eliminate all local gun ordinances, including Chicago's current ban on assault weapons, but would curb local control on handguns and lawful transportation of firearms.
The Associated Press contributed to this report.