CHICAGO — An off-duty Cook County Sheriff working security at Millennium Park shot a man after the man fired a gun Friday evening, Chicago police said. Around 7:20 p.m., a man in his early 20′s refused to be wanded at the entrance of Millennium Park, the Chicago Police Department said in a media notification. The man jumped a fence and as security approached him he turned and fired, police said. An off-duty Cook County Sheriff’s officer working security at the park returned fire and struck the man, police said. The man then ran toward the 300 block of East Riverwalk where he was taken into cus…