There were two military helos doing laps very close around the top of Lambeau Field (Green Bay Packers) stadium starting at about 6 minutes into the 8/16/18 game against the Steelers. Not Chinooks, but very out of the ordinary
Police are investigating this surprise flyover
https://www.wbay.com/content/news/Police-investigating-after-surprise-flyover-of-Navy-Helicopters–491135941.html