By Philissa Cramer A klezmer band was playing when a shooting interrupted a Fourth of July parade in a suburb of Chicago Monday, killing at least six people and sending dozens more to local hospitals. A congregant and staff member of a local synagogue was among those murdered, the synagogue announced Monday night. The mass shooting in Highland Park, Illinois, one of the most heavily Jewish suburbs in the Chicago area, is at least the 300th in the United States this year. Eight hours after the shooting, law enforcement authorities said they had arrested a person of interest, a 21-year-old...