A 91-year-old civil rights activist and education advocate was stabbed multiple times while walking her dog in a Boston park, authorities said. Jean McGuire, the first Black woman to serve on the Boston School Committee, was stabbed in Franklin Park at about 8:30 p.m.Tuesday, Suffolk District Attorney Kevin Hayden said Wednesday after visiting McGuire at the hospital. McGuire's stabbing, as well as the recent fatal shooting of a 14-year-old boy in the city, is unacceptable, said Hayden, whose family has been close to McGuire's for years.