A 65-year-old retired probation officer from Chicago fatally shot her grandchild’s mother on an Upper East Side street Friday just yards from Gracie Mansion, then turned the gun on herself, NYPD detectives said.Kathleen Leigh shot Marisa Galloway, 45, on E. 88th St. near York Ave. at about 8:50 a.m., then killed herself in an apparent…
