Severe thunderstorms sweeping through the U.S. Midwest have killed a motorist in Michigan, shattered windows in an iconic Chicago skyscraper and knocked out power to hundreds of thousands of people. Sheriff's officials said a driver was killed near Dexter, Michigan, about 40 miles (65 kilometers) west of Detroit, when winds toppled a tree onto a vehicle. In Chicago, powerful winds and heavy rains broke windows in the 110-story Willis Tower. The debris looked like icicles falling from the skyscraper, formerly known as Sears Tower, AP quoted witnesses as saying. Utility officials said power is out for about 215,000 Chicago-area customers and 150,000 in Michigan.