CHICAGO — Mayor Nancy Rotering had just started walking in Highland Park’s Independence Day parade when the music from the high school’s marching band ended abruptly, replaced by an ominous cadence. “I didn’t realize it at the time, but what I was hearing was the gunshots,” she said. An instant later, spectators and marchers bolted from the noise and first responders ran toward it as the terrible realization struck that the North Shore town was under attack. Rotering and others screamed at the crowd to leave as a rooftop sniper fired dozens of shots, killing seven people and wounding more than…
