SUN PRAIRIE, Wis. – A firefighter was killed and at least a dozen other people were injured when a natural gas explosion leveled at least two buildings in a Wisconsin community, authorities said Wednesday. A gas leak in downtown Sun Prairie led to an explosion Tuesday evening that destroyed several buildings and ignited a fire that sent billowing smoke that could be seen for miles around. Another firefighter suffered critical injuries in the blast but his condition has been stabilized, according to Sun Prairie Police Lt.