WASHINGTON (WPVI) — The hit-and-run driver accused of killing a Philadelphia man in Washington D.C last summer has been formally charged.Benjamin Robertson was indicted Wednesday by a grand jury in DC.On July 12, 2023, Robertson was fleeing the Secret Service when he struck 75-year-old Bing Wong and his 13-year-old step-granddaughter.Fortunately, the teen walked away with…